could be
I'd look at it this way---has she had a seizure everytime she's taken OTC? Were the OTC's the same each time or were they different types of OTC? Or has she only taken the OTC those couple of times? Also did she take OTC while on AED's and have or have not had seizures as a result? Did she only get seizures when she wasn't on AEDS and took the OTC?
I think it's possible to have severe reactions to any med you take AND I'd say that a seizure would be considered a severe reaction. Some people are allergic to many things and it is possible her body can't tolerate it. On the other side, if she's only seized while taking OTC on those two occasions and she's taken OTC other times with no reaction, I would think the seizures occured as a coincidence.
Perhaps it isn't the meds but the virus or bacteria or fever that is producing the seizures?
In order to really know, you'd probably have to keep a journal of what she eats, her moods, how much sleep she gets, what meds she takes, etc. Then look for any patterns. I'd also bring it up with her doctor. He may want to do some bloodwork, an EEG, or MRI. Also perhaps have the allergy scratch test done and see what allergies she has.
Good luck,