I agree with Tommy, she's probably a yearling at that size. I've heard of females breeding that young, but it's pretty unlikely especially at that size.

For food I've noticed even individuals of the same species will have preferences, and then suddenly decide they want to eat something else. Trying different things until you find what she really likes is best IMO.
Also, are you looking at fish as a potential food source? I ask because there is a lot of debate over the safety of various species of fish and sources of fish, and potentially even negative effects of a fish heavy diet even if you stick to safe species. That sort of thing isn't mentioned on a lot of online caresheets, so I'm sure everyone here would be happy to give you info on that if you're curious.