Technically, yes. It would be classified as taking another persons prescribed medications, which would be the same as if u would have taken one of her Hydrocodone or Oxycontin tablets. It may or may not have a big impact on the background check, but I would be honest with the investigators, & make them aware of the circumstances by which u took the meds.
To expand on this for the people who do not get it.. It is not what the content of the medication that he has taken that is at issue, it is the fact that Ibuprofen, in an 800 MG tablet, is only available with a doctors prescription. If u took 4 of the 200 mg tablets, which r over the counter, u get the same effect, which is obvious. But taking someone elses prescription is illegal, there is no denying it.