If it were me, I wouldn’t say anything to such a parent because this girl’s medical care and this family’s reception of Communion in light of that medical care is not something I should comment on. To answer the implied question, if the drug ordinarily used for contraceptive purposes is used instead for actual therapeutic purposes such as irregular periods, there is not a moral problem with taking it for those therapeutic purposes. It would be better to consult a pro-life, pro-NFP physician for alternative treatments, both for medical and prudential reasons, but doing so is not required. Someone who wants to do so should call the Pope Paul VI Institute for assistance.
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.