I would bet if you gave that snake a 60ish gram (small rat) every week for about 2 months she will be up in the 500's without a problem.
To be realistic that snake can prob take down a rat up to 75-80 grams. Now she will look like a sausage but she is fattened up.
To be honest it's MUCH better to wait on normal sized meals until she is up to size rather than "fatten her up". If your planning on breeding, fat = slugs, which means no babies for you.