Rat Breeder/ Feeding SOS

[BURMS]

Hi all, I have a 7 month old burm and I've been feeding her small rats once a week, but they only left a bump in her for about 12 hrs, so today I decided to try to feed her a medium rat which she took and ate happily, so I think I will switch to medium rats but I want to know how often to feed her since she will be eating larger meals. Secondly, I am looking for a new feeder rat breeder that is reliable, has good quality rats and not too expensive. The problem is that I am looking through various websites and small rat weights 44-84 grams, while a medium rat weighs 84-174 grams. As you can see, there is a huge difference between the weight of the rats, and the medium rat she just ate weighed 90 grams... What should I do???

Any help is greatly appreciated!
Thanks!