Won't eat, will not eat, refuses to eat, doesn't want to eat...blah blah blah

One thing that I haven't seen mentioned is to try scenting a rat with gerbil smell. Find someplace that has gerbils and ask for some soiled substrate. Let the rat live in that overnight and then try feeding the rat to your snake.

One thing I'm a little concerned about - You said the snake is 4.5 - 5 feet long (an adult), its only eaten once in 2.5 months, and has shed THREE times? An adult won't usually shed that frequently unless there's something wrong. Does she have any injuries? Have you checked for mites?

Steve