I don't believe you have much to worry about. I have been swimming at least once a week, frequently more in the summer, in both lakes and indoor pools. I have not encountered any problems related to this. In fact, it has contributed as a great form of exercise for me and I have been in my best health in the last 5 years in this time. I am on a remicade and aza, and although these do reduce immune responses, I have not had problems. If your girl can do the swimming, I would say go for it!