I wouldn't hold what they say in too much regard... Unless she came from a very reputable breeder. As said above, One good size medium rat is probably enough for her every week to 10 days. Don't worry about the aggression, it will fade. Keeping her on a set regular feeding schedule of one appropriate sized feeder is the best thing for her. Feeding her regularly, and letting her be (no handling) for a couple of weeks may be the best option.