New female hates being handled

[Macropodus]

... she hates being handled. She hisses and she's lunged at me twice and for some reason she prefers my girlfriend handling her. She will ball up tight if anyone goes near her enclosure (unless it's my girlfriend) and hiss. ... Any ideas to get her used to being handled without worrying if she's going to bite? ... Any ideas? ...

You say "for some reason she prefers my girlfriend handling her." Well, identify that reason and practice it. Sounds like a handler problem more than a snake problem. Try having her handled like the girlfriend handles her, i.e. "without worrying if she's going to bite." It's a Ball Python not a SaberToothTiger.