Keep a teething toy handy, and every time she goes to bite put the toy to her mouth so she learns to bite what she is supposed to bite.
The fluid filled ones that you refrigerate prior to use are often favored by young kids. Break bad habits by replacing them with good ones.
You might also try giving her a pacifier. I know there are various arguments against them, but especially right now I would see the greater good in letting her use one.