I think that you shouldn't be the one to bring the diapers up again. If she mentions it again, you can tell her that the added stress of being in college, and mid terms, and trying to get good grades to make your parents proud, has caused you to have a couple of accidents. Tell her you went to the doctor at your school, and they said it is more common than people think. You can then say that there is nothing to worry about, and possibly pull up a couple of websites about stress incontinence. You can also tell her that you don't tell her or feel like talking about it, since you are embarrassed.