It would be much better to just wait on breeding and mice do perfectly fine in raising snakes up. Whatever she eats with gusto each and every week, feed that. She could probably do a third mouse if you want.
I prefer the females to be at least 1500g if not more. I look at their body type. Short and fat 1500 grams and they can go. Long and thin 1500 grams, then no, I'll wait. Should be about 500g per foot, so a 4ft snake should be around 2000g before I feel comfortable breeding her.