To cut my backstory short: we adopted two feral cats in April. They're incredibly shy. In October, we adopted another feral cat (we took him in from the street). The third cat is the most extraverted cat I've ever seen, he approached our girls immediately and they obviously did not like that.
Everything I mention is based on our experiences, which have yielded good results so far. They're socialized, and although the older ones can't quite keep up with the younger one's playful nature, they're at least considering each other as part of the same family now.
i) How do I gain that feral kitten's trust so that I can pet her and hold her?
It takes time. Not every cat trusts you as quickly.
Getting a shy cat (or person) to trust you, is the figurative variant of dipping your toe in the water before you jump in. Start off small, make sure the experiences are positive, and you'll see their confidence grow with every new positive experience they encounter.
This is what we did:
- When feeding the cat, try to pet her. Very slowly bring your hand forward, in a way that the cat sees your hand approach her.
- If she doesn't see it, abort mission. Only touch if she knows you're going to touch. Don't startle her.
- She will likely recoil when you touch her (or even just reach for her). That's normal. In response, you disengage. Look away, do not stare at her. Let her eat in peace.
- After a while, you can try again. I generally try to space my attempts so that I can try to pet them 5 times over the course of a meal.
- The intention is for them to see you try the same thing over and over. Eventually, they'll learn a few key things:
- You're not trying to hurt them.
- You really want to pet them (since you keep trying)
- Eventually, the inconvenience of recoiling and not eating will no longer outweigh the inconvenience of being pet by you. Once you reach that point, they should at least allow you to pet them, even if they don't like it.
- If their experiences with being pet are never negative memories, then they'll eventually don't mind you petting them because they know it's a harmless action that pleases you.
- For food, you were somewhat required to make sure she still eats and doesn't just run away in fear. However, treats are more lenient. As she doesn't need treats, you can get away with refusing to give treats if she doesn't allow you to pet her (you can't take away her food).
- Try using small treats. You're better off giving her 3 small treats instead of 1 treat that's three times as big, because every single treat will be a learning experience.
- I used to give them the first treat for free. The second treat would come at a cost:
- If they allowed me to pet them, they would immediately get a new treat.
- If they don't allow me to pet them, then there was a 30 second timer, after which they'd get the next treat. When they've been making progress (e.g. allowing the occasional pet), then I would start making the timer longer, to incentivize them to focus on the petting.
- One of them was a bit apprehensive of petting, but she did make an effort in coming forward and sniffing (and later licking) my hand. That was equally rewarded with a treat, it's the effort that counts.
- Repeat until they've had enough treats.
Those are the easiest ways to get them to allow you to pet them faster. There's not much else you can do, other than trying to pet them once (and if they refuse, leave them be).
ii) Why isn't she ready to get picked even when she's been staying and eating at our place since 3 months (She comes close only to eat and then goes and sits in the carton box)?
Not every cat wants attention. Humans can be introverts or extraverts, and cats are no different.
I wish I could show you my current cats, because they are as different as day and night. One of them defaults to being apprehensive of everything and observing at a distance until she knows it's safe, another defaults to coming forwards (but if something bad happens, she'll stay way from it for a looooong time), the younger one just engages whatever has caught his attention (without fear or apprehension).
Also notice that if you give her everything she wants (food, a sleeping spot, solitude), and you expect nothing in return (initially, because you expect that she'll eventually want attention when she feels more at home); then the cat will settle into that agreement. If they don't really want attention, they'll never come looking for it.
Instead, if you want to create a bond with them; you should put a price tag on what you provide for them. This ties into the earlier point, e.g. teaching them that they get more treats (or get them faster) if they allow you to pet them.
Do not starve your cat. Only put a price on optional things like treats and toys. Do not withhold food or shelter from them, because that is not a positive experience.
For our girls, we only managed for them to allow us to pet them. They never came looking for attention by themselves. They did come for treats, but never just for attention.
Until we adopted the younger one. Because he's an incredibly social cat, he approached us whenever he felt like it. And he would get a lot of love from us. This did not go unnoticed. The other two cats had never even considered coming near us (unless there were treats); but after they saw the young one do it and get love and attention (with no negative side effects whatsoever), they were incentivized to overcome their apprehension and clearly started repeating his behavior (they even copied his behavior such as swatting their tails in our faces; something they never did but he always does).
iii) How do I make her friendly with the new kittens?
There is no guaranteed method. There are myriad reasons why cats may not get along. Some are easy to overcome (e.g. first impressions), others may be impossible to overcome (e.g. bad past experiences that have left emotional scars).
All you can do is make it easier for them to see each other as friends.
- A tired cat does not have the energy to pick a fight or get antsy for no good reason. Since you have kittens, this will be the strongest tool in your arsenal. Get them to play (even if separately), and tire them out if you can. The more exhausted they are, the less they will get antsy when another cat comes near.
- There's a reason why "breaking bread" is often used to imply "social bonding". It humanizes (felinizes?) both parties, they see each other as creatures that need to eat to survive. The need for eating is a shared life experience.
- Feed them at the same time, next to each other.
- If that's not possible, keep them further apart, but keep them in sight of each other.
- If they are not able to peacefully eat in the same room, try putting a glass separator between them (so they feel more at ease, but still see each other eating.
- Make sure you give them ample food. There needs to be more food than they can eat; simply to prevent any feelings of resentment that the other cat is eating food that they'd like to eat.
- Our vet confirmed that it's better to give them too much food for a short while; and have them bond more easily; compared to keeping them on a strict diet and indirectly adding social tension between them.
- Similarly, give treats in a round robin fashion. One for A, one for B. It may seem childish; but this is the best way to make your cats understand that they are equals. If you give a handful of treats to one of them, and give it to another cat the next time, then they may not realize that they're getting their fair share, because they constantly see an unfair division of treats (in the short term).
- Get them acquainted with each other's smells.
- Pet them with the same hand, to transfer their smell onto each other.
- We kept our cats separated at night (the youngling wasn't fixed yet). Since they each had their own toys/blankets, we set up an "exchange" program. We would occasionally swap some toys/blanket, just to get them acquainted with each other's smell even if they weren't in the room.
- Try to find mutual interests. Two of our cats loved the laser pointer so much that they couldn't stay away from it (even if the other one was also there). Although they were selfish in the beginning, I made sure to put them on equal footing (making the older one more playful, making the younger one less energetic by tiring him out).
- It took about two weeks, but they eventually evolved towards playing with the laser in turns (so that the other could have a quick rest).
- Note that I didn't tell them to play together. I just knew that they'd both want to play, which means that they forced themselves into a situation where they were going to need to get along without bothering each other.
- If the cats are uneasy around each other, make yourself the center of attention. If they're both focusing on you, they're not focusing on each other.
- Feel free to be silly. I have a habit of singing while I'm cleaning; and I've seen the cats share looks about my weird behavior. That creates a bit of rapport between the cats (by making myself the odd one out, I make them see each other as "not the odd one").
That's about all we did, and we've bridged most of the gap between them in about two months' time. Although there's still some awkwardness from time to time; the cats are no longer obstacles to each other.
I wish you the best of luck :) It may be hard and feel like it's pointless in the beginning, but I expect you'll agree that it was worth it once they finally get along.