She's probably fine, and is just cleaning herself a little vigorously. As the vet said, if it doesn't look sore there's probably no problem, although if you're really concerned you could look into skin allergies (although these are exceptionally rare) or dust irritation caused by the cage lining. To rule out the latter simply line the cage with sheets of newspaper, and if the behaviour stops you've found your cause. Most stressed birds pull out their feathers, so this is the main sign to watch out for. She could be simply bored, so if you haven't already done so try putting mirrors and toys in the cage. As for her mate, firstly as it is impossible to sex birds without a blood test you may have got two males, in which case they will squabble, but most birds, regardless of gender, will usually get along fine; the occasional fight is only to be expected and as long as neither is getting badly hurt there is nothing abnormal about their behaviour.