Cats are creatures of habit and don't like change. Over-stimulation sounds like the issue. Body language is a good thing to pay attention to. If her ears start to go flat while you're petting/brushing her, (we refer to them as "airplane ears), that's a sign of over-stimulation. Stop and let her be. She getting used to a new environment and being loved, two things that are very foreign to her. Let her come to you. It may take some time, but she'll come around. Just be patient. Have treats on hand. Sit down on the floor with her and toss them to her. See how fast you two will bond.

If scratching or biting is STILL an issue, keep a squirt bottle on hand.