I would go with the live rat on her next regularly scheduled feeding day, but I second that at her size a small would be more than enough. I have a female spider, that is about the same size and age as yours, and I fed her average sized smalls 95% of the time. She did take a medium once when a larger girl didn't want to eat but that was the only time, and she skipped her next meal because her that one had been so large. Do you have any pictures of your girl that you could post here? I have a male that hasn't eaten this calendar year but up until late November he had been slamming small rats on the regular. This time of year does it to them, for sure.