A.S.
It sounds cruel, but I've heard a lot of people say that the only way they could get their child to stop biting and pinching was to bite them and pinch them back. They don't really understand how much it hurts, they just know they get attention when they do it.
My only other suggestion would be to completely ignore her when she does something like that and talk exclusively to her brother. "Oh, buddy, what's wrong? Did sissy bite you again? That wasn't very nice of her, was it? Come here and let me hug you, would you like a treat to take your mind off the pain?" And just completely look right over her, don't even acknowledge that she is in the room. Later, once your son (and you) have calmed down, remind her that biting and pinching are mean, and ask her if she want's to be a mean person, or a nice person. Try to figure out what prompts the biting and pinching. Is she jealous of him? Is he playing with a toy she wants? Once you figure out what is causing the bad behaviour, give her alternate ways to handle the situation. Bubby has your toy, ask nicely if he will give it back. If he won't, is there something else you could play with until he gets bored with it? When she gets mad at him, encourage her to come discuss her feelings with you in a "big girl" way. That will not only help her learn to deal with anger, it will give her some much needed one on one time with you.