bit off topicish but my friend and i have always had pet rats. i feed mine on fruit and the petshop rat mix, she fed those two plus meatie bites.
her rats went feral and either tried to eat you (aggressivly not cute) or anything else in their path. mine is still perfect. my friend has had several rats after her first one went spacky and they all somehow kill themselves. mine is still going strong.
so we put the meat in the diet down to producing the abnormaly aggressive behaviour. but these are pet shop rats so they might just be inbred to many times. strange though that mine is fine and never aggressive. but even if this were a possibility i doubt your female would be able to chew her own ears off... strange