A nice normal rescue! Congrats and welcome to bps! If it will eat rats I would switch it over. IMO their excuse as to why she won't eat rats is bogus. If you feed live the snake will get bit every now and again. Rats/mice have teeth, there's no way around it. Usually the bites are harmless, few do much damage unless the rodent is left in the cage.

As for sexing there is no real way to tell other than probbing/popping. Popping at that size is extremely hard for someone that doesn't know how, or is new to popping. I would find a breeder in your area and ask them if they would be willing to pop/probe.