She should ask the doctor that is prescribing her medications or her pharmacist, point blank.

I was on a medication (triliptal) for at least a year that interacted with my birth control. I had two different doctors prescribe it to me. It was when I went to my third pdoc, who called it into the pharmacy and was told by the pharmacist that it was interacting with my birth control. She then called and told me, and I was amazed to find out. Luckily, I wasn't sexually active at the time... I don't think it was listed in the paper work that comes with the medications because I used to read those religiously.

I also know that St. John's Wort makes the birth control pill less effective (I'm not sure about other contraceptives).

Definitely have her talk to her doctor or pharmacist.