As far as I remember, initialy when you have lunch with her in the cafeteria and tell her your backstory, she decides if you are a good person and recomends you to Jill. Dont remember every choice, but wearing the dildo helmet detracts points, so does making fun of cafeteria girl's food, beating up Troy in ep1. Oferring to pay for her food, helping the kid in the math class with homework and not giving a smartass responss to Jade when she asks you why are you taking Gender Classes, makes both of them praising you and Bella likes that. If you pass that checkpoint you will eventualy get an option to visit her in the library, which is the point where you basically open her path. After that you should be able to move in with her when Josy shows up at @ Maya's.
In ep 5 dont sleep with Cathy, as that closes her path.
You dont need any specific affinity, or status, just be carefull, especially early on DIK MC joke options are very crude and Bella doesn't lile that. By not going CHIck you miss out 2 extra possitions on sex scenes with her, one is 69 and I forgot the other one.