P.M.
One of the most effective things I have used with very young children when they are acting out of stress is to smile, scoop them up in a big, gentle hug, and say, "I love you, and I can't let you do that to me!" The child may either melt into the hug or struggle to get away, along with sound effects.
In case of struggle, particularly if she tries to hit again, hold her arms down for a little longer and say, "If you don't want me to hold our arms down, don't hit me! Every time you hit, I will hold you like this, because I don't want you to hurt me!"
Keep the mood light, cheerful and matter-of-fact. Be completely consistent. Never be angry; you don't want her to think she has the power to manipulate your reactions, and you don't want to add to her stress. And children who are acting out are feeling stress over the behavior, in addition to whatever is making them upset in the first place. They know hitting (biting/kicking) is wrong. Your ability to absorb the negativity and give love back is very reassuring, and models a response pattern they will start to copy as they mature.
When she stops struggling (and maybe yelling or crying), tell her you will always do your best to keep her from hurting other people, because that's what mommies are supposed to do for their children. Tell her you know she will learn to stop hitting, and then you won't have to hold her like this. But be prepared to do this over the next few weeks, until the changes that are upsetting her have stopped and she has a chance to adjust.
This gentle, consistent response gets through to an upset child in a way that time-outs can't match. Even if it appears to increase the upset for a time, it is more reassuring than sending her off to be by herself, which could feel like exile or rejection. This proves to her, over and over, that you are there for her. You are not coddling her.
You can also help with her general anxiety by taking every possibly opportunity to relax, talk and laugh with her. Keep her informed about what is going on and the projected time line. She probably understands more than you think.
I learned this technique from a very successful child-care worker who used it with some very troubled kids. They all ended up loving and trusting him, even though the process sometimes appeared to aggravate them at the beginning.