It depends what pill she is on. Do some research on her particular BC pill to find out what the hormone levels are. Some pills give you the same dosage for 3 weeks, some pills go up and down with hormone levels. Some pills I found make me more emotional like crying over stupid stuff, some make me more testy and angry, others make me break out with acne, and other make me feel totally bloated. It's an individual thing. But emotions, and some people are on emotional roller coasters on it; are a definite side effect. Weight gain can be also. Although my doctor said that through studies it has been proven that BC pills don't make you gain weight. I guess I'm different every time I went on the pill I tacked on 5 pounds, when I go off of them the weight comes off. So you'll just have to see how she reacts to them, do your research, and talk to her and ask her what she thinks.