It could be a side effect of her meds (check with your vet on that one), and they could be due to her having an irritation and scratching, and biting, and worrying it til the hair got rubbed off. Are they just bald, or do they look like a sore? If they look like a sore, they could be hot spots. But I'd call your vet and see if it could have something to do with the medication.