Hi, and welcome to BP.net!

Ball Pythons sometimes will just bite down on you. I've heard that they just slowly do it, and sit there for awhile. I've never had it done to me, although I sort of wish one of mine would. I hear it's pretty funny!

When you say lightly biting, do you mean she is "chomping" so to speak?

How old is she, and what are you feeding her? What type of enclosure is she in, and what are the temps/humidity?