If my snake skips a meal, I just wait another 5-7 days and try again. I've never had persistent problems with my snake eatting mice or rats, and I've gone back and forth depending on the supply at the pet store.

My favorite phrase in the kitchen is "Hunger is the best spice". I guess that's not the best thing to say when you're the chef...but I'll go out on a limb and say your snake will eat that rat if she decided to skip her last meal or two lol.

Have you tried smaller rats like a pup or weanling? My snake is about the same size as yours, and even a weanling is hit or miss on whether it's too big for her, so I stick with rat pups or weanlings that I can inspect before I purchase; If not, it's mice all the way until she's a little bigger.