Hey Marissa!
Generally BPs in the wild eat Gerbils however depending on where you live it may be illegal to feed gerbils to your BP. A lot of people will say that rats are better because they resemble the color of gerbils (brown vs white) however this is an opinion I believe.
Most people move to rats and ween off of mice because once your BP gets big enough you will want to feed rats instead of having to feed multiple adult mice to give your snake what it needs. I would say if you have your BP on rats, to leave her there
Hope that helps!