You could try ‘slow blinking’ (which is closing your eyes for several seconds, say 4 or 5 seconds or even longer, then opening them again for say one or 2 or 3 seconds and then closing them again, and so on. Just make sure your eyes are closed for longer than they are open each time.) All felines sleep a lot - which makes them vulnerable to being attacked and also they tend to avoid other cats, unless they think the other cats are a part of their group or family - and so slow blinking at any cat (or human or other animal) is their way of saying, “I trust you and you trust me enough that we can go to sleep without having to worry that one of us will attack the other.” Maybe it has something to do with ‘mirror neurons’ - I’m not sure, but such neurons do apparently have something to do with mirroring back/empathising with? what others do - but I know it works. My adopted cat was returned to the RSPCA by his two previous adopters as he was too aggressive. And although he has very occasional regressions, 99% of the time now he is beautifully behaved and very relaxed and happy with me. I have had him for 3 yrs now. One of the techniques I use with him (as a daily routine thing, as well as if he is having a regressive episode, which he sometimes does) is the ‘slow blinking’ technique of building trust and fostering relaxation. He will start to slow blink back. (If the cat you are trying to help, doesn’t respond at first, just persist.) It seems to have a fairly immediate hypnotic effect on my cat now ... but also it has an accumulative effect over time of just making him calmer overall. (I also combine it, as soon as he starts to slow blink back at me, with something in a gentle tone of voice and repeating it a few times, which also seems to add to the relaxing effect, eg ‘’sleepy cat, good cat, sleepy cat, good cat ...”) Hope it helps. Also, I don’t think the way the cat hisses at you, but not your family, is a bad sign. On the contrary, the cat WANTS TO be friends with you (as shown by her coming forward) But is just afraid to do so (as shown by her hissing.) The two opposing reactions just means she is conflicted and trying to decide. With the other people she is not trying to make up her mind; she already knows it is best to flee from them!
(But still it would be good if you could encourage even one of the other members to also make friends with the cat ... but only after you already have, I think. For example, after you get the ‘slow blink’ communication going with the cat, you could ask a child to come and sit and slow blink at the cat too. Do it in a way that helps them to be fascinated by ‘the complexity of life and relationships’ for example and how that extends to how animals relate too. Help them to marvel at some aspect of life’s complexity, rather than it be something they want to control, or are, themselves, afraid of. But make sure it is someone who YOU trust will not get the cat’s trust and betray it for some reason. If that is likely to happen, just befriend the cat yourself. Otherwise, if you introduce her to someone else and then something bad happens while that person is with you and the cat, the cat might end up up not fully trusting you either.)