We don't really know an awful lot about Jane Rochford. People paint her as a bitch based on the fact that she gave evidence against her own husband and Anne, and as a bit salacious and creepy based on the fact that she seems to have helped the young Katherine Howard to meet her lover, but there's another view that she was just a bit of a people-pleaser who found it hard to say no to anyone, and that she might have been put under pressure in the interrogation over Anne (no-one is suggesting torture or anything, but it would be a scary situation and you might well agree to say things).
There was a biography of her a few years ago but the main criticism of it that I've seen is that because we know so little, it inevitably falls back on generalising most of the time in a 'as a Tudor woman, Jane would have done this...' sort of way because there isn't enough specific stuff to say.