Do you know how much she weighed when you paired her? I wouldn't breed a girl under 200 grams.
Also, "large" isn't a very good measurement... they could be anywhere from 6 months to a year old depending on how often your store sells rats and females should really be bred before they are 9 months old.
If she has another small litter, I wouldn't keep her as a breeder.
I recorded a weight that I think is from shortly after I paired her and it was 190 grams. Maybe she was just a little too young.
