I had the same problem, but I did a few things that made ALL my snakes pound rats. First of all, I started feeding smaller rats. Not very small, just slightly smaller than usual. And every day that I'm feeding, I get out the frozen rats in the morning and let them thaw in the snake room. When I get home from work, I clean all tubs. I don't know why, but I think the snakes get used to this ritual and get into feeding mode. Later that evening, when it's dark, I put on a very small light in the snake room and feed the snakes.

This is what works for me. Give it a try, I'm pretty sure your girl will get up to weight!