TL;DR
I don't think there's a problem here, just normal cat behavior.
Tangentially
About half a year ago, we adopted two sister cats. They were born as feral cats, living in a prison building. Because the guards would remove cats when they encountered them (this happened to siblings of theirs, who they never saw again), the cats were incentivized to be quiet and shy away from all human contact.
Interestingly, there is a lot of overlap with your cat's behavior:
She now hides on top of the fridge all day, specifically hiding under the cabinet.
Ours hid in cardboard boxes, but I think their intention is the same: seeking a safe spot that's out of sight.
She finally opened up enough just two days ago to let me pet her, and she purrs a storm, but she will take my finger and lightly bite it.
One of the cats does the same thing. She lightly bites my finger/arm whenever I pet her and she really likes it. I have also noticed that she bites her sister when they are giving each other love.
So the message is clear: soft bites are a sign of affection to that cat.
Interestingly, her sister shows affection through licking instead of biting. She licks her sister, but also resorts to licking us (my hand, my back, even my armpit...) when she's very happy with us. This can occur during petting, but also after we've giving them food or treats.
But both cats are adamant about their way of giving affection. The licker never bites, and the biter never licks.
She will also follow my hand as I pull it back from her spot, but only if at least half of her body is hidden.
Especially in the beginning, we were only allowed to pet their "first half". Touching their second half would cause them to leave (initially, they were fearful; after a while, they looked uncomfortable but not afraid).
That has changed by now, we can pet them on their entire back. However, they're still not a fan of belly rubs, and they will generally nudge my hand back to stroking the back of their neck instead of having me stroke their back.
Finally, when I pet her, she stretches out her paws and paws at the air, because when I pet her she usually falls to her side or on her back.
This is where I need to differentiate between the sisters.
One of them was the "extravert" (compared to her sister). She would be the first to try something new, while her sister observed at a distance. She was the first to come to us for petting, and many other milestones.
This cat, although she asks for petting more, has a habit of keeping a blank stare. She positions herself ideally for pets (e.g. in front of my feet), and will purr, but she looks like she doesn't care at all. She never shows enjoyment of the petting, it's only obvious by seeing her not walking away.
The other one, although much more apprehensive initially, is unable to hide her excitement. Whenever she knows that she's going to get something she likes (pets, treats, toys), she makes a happy "prrrrp" sound and arches her shoulders, up to a point where her front paws leave the ground.
She is literally incapable of suppressing that reflex, which makes it doubly as cute.
A direct answer to your question
So back to the question, she decided to step out from the cabinet to groom herself after a long session of petting, but when I went up to use the restroom she ran back into hiding. She does this all the time, if I move around her she runs to hide. Is this normal behavior, especially after she wants to be played with?
There are two options here:
Initially, our cats would immediately freeze when we moved. This ties back into them wanting to avoid human attention (from the prison guards). Whenever one of us moved, they would stop and stare (and hide, if they weren't frozen by fear). And they would remain still for minutes afterwards.
They eventually got over that. We took some steps to improve it, but it's also possible that the problem fixed itself over time, regardless of our steps.
If your cat is hiding out of fear, you can try the same steps to make her feel at ease more.
- Move slowly.
- Always start off with a small movement before resorting to bigger movement. E.g. before standing up, drag your feet across the ground for a second or two. It alerts the cat that movement is happening, without immediately making a big move that startles them.
- Avoid eye contact. I've learned that when you look at a cat, it generally thinks that your current actions are directed towards the cat. If I make eye contact with my cat (just to say hi) when I pass her in the hallway, she will move out of the way, as if I'm coming for her. When I do the same without making eye contact, she doesn't move out of the way.
Secondly, running and hiding may be part of playing. When our cats play together, they tend to "play pounce" on each other. They'll run out of sight; sneak up on their sister, and then quickly run towards them and fake pounce (landing next to them instead of on top of them). This is the preferred method of playing between the sisters.
We also have a third cat, who prefers wrestling more. He doesn't stalk or pounce, he simply attacks with a flurry of paws. The sisters still try to run out of sight and sneak up on him, but he has a habit of chasing them, therefore making it impossible for them to actually sneak up on him.
