If you have only just moved her next to another cage of rats, it could be aggravating her a little.
Has she been on her own since you've had her? Perhaps she would improve with a cage mate? I know our two came on leaps and bounds when we were eventually able to put them together (after quarantine and introductions, etc).
Our eldest, who was also a bit of a biter, has also improved dramatically since we decided to trust her and have her out on the couch with us, for playtimes. When we first started having her out on the couch, we couldn't even pick her up very easily. It only took a few days before she would let me pick her up to put her back in her cage, when she was tired. Now, after just a few weeks, she will sit in my lap or the crook of my arm and let me scratch her back and whatnot... only for a minute or so, mind you, being a wriggly female and all! :lol:
It's hard to say without knowing your rat, but perhaps she is just a bit frustrated and needs you to take a chance on her? Also, if frustration is the issue, adding/changing chew toys in her cage might help...