Do you have wand toys she's interested in and will chase after, as these can be quite good for playing in an interactive way without needing to make actual contact, but still be able to touch Sofie gently say on her head or back when she is tired out and resting - try and find out which bits she is OK about being touched and which bits she's not. Another good thing to do might be to try throwing dry food for her to chase so it is more directly associated with you, and not to leave food out all the time but put it down at set times and you can start to try and sit near her as she eats. Almost like introducing a new cat in to your home and starting to build up trust?
Idea being to play with her as much as you can without actual physical contact (unless she invites stroking and is calm), and for her to start to re-associate people one at a time as safe and friendly. That she has plenty of play and activity using her cat hunting skills so hopefully some of her excess energy and stress can be released appropriately and not through biting people. If she wants to be physically close and biting let her do it with something you are holding like a cuddly toy or a Kong.
If she does bite, try to follow the advice on the biting threads, to use a single word firmly but not shouting, freeze and if anything push very gently in towards her as she bites or wraps her self round you so she doesn't misinterpret anything as fear, attack or wanting to play fight, and stay still until she lets go. Repeat the 'no' or 'ow' or what ever word you use if you need to. Don't try and remove her unless she is breaking skin and causing actual harm. If there is no movement she will usually give up. If you react it encourages behaviour and teaches her that is how to get attention. Save your reactions for things you want her to continue doing. Try if you can to explain this to other people in the house too, whether it is family of friends, so she can get as consistent response from everyone as is possible.
If you have already tried all these things let me know.
Do you have any fishing rod or wand toys that you can move gently and coax her in? No sudden, big movements of your arms and hands, just something you can move about a little way away from you that she might like? You can even tie little toy mice and things on the ribbon or string and pull them across the floor in short, occasional twitching movements to try and catch her eye? If she isn't ready for that try with the being around for feeding her first. Warning, if you use ribbon or string don't leave it out as cats have a habit of eating it and it gets tangled in their gut making them dangerously ill.
It might seem drastic but it might be worth you looking at some of the threads in the caring for strays and ferals forum because there's a lot of stuff about how to build up trust with very wary, frightened cats in there. People have come up with some amazing ways to build trust, and regain trust when they have done something inadvertantly that has set a cat back so it has gone in to hiding again.
I really think your cat needs to see a vet to rule out any physical problems. Suddenly starting to bite is a sign of a problem. Can you take her to the vet yourself? How old are you?
Is your brother younger or older than you? I am asking because I wondered if you are able to tell him to stop doing bad things to the cat. Can your parents not stop him? As for most of the other things, they are all normal for pet cats and should not cause more than a short period of stress. I agree that a vet visit is a good idea at this stage.
my brother has stopped being mean and he is older and we found out she was just bored so we are going to take her to the vet any way and does anybody know about turtles because mine has been sleeping too much and has not been eating at all
Good to hear things have settled a bit between younger brother and cat, keep us updated on how things go and what the vet thinks. Hopefully no health problems and all a matter of rebuilding trust and lots of play.
Happy to see molldee on here as a turle person on here coz I know nothing about them!