Because she was whacked out on Flexeril and booze? That said, I'm not saying this is what happened. I just have to wonder why she would be prescribed a muscle relaxant. With her alleged history, that is.
Flexeril isn't a heavy-duty narcotic. It's not a recreational drug that's subject to wide abuse and would not be difficult to get a prescription for, nor would it be a drug that someone would want to avoid using. It's just that it causes dizziness when combined with booze, which is what she did. Neither is an illegal substance, so there was no big deal in her admitting that she used it. I doubt that she didn't have a prescription for it.
What does her alleged history have to do with anything pertaining to the Flexeril? We don't know anything about her other medical history except that she was fit enough to be accepted into the Navy and that she had two kids. Flexeril is no big deal, and could easily have been prescribed for ner by a doctor for some muscle strain or back pain, any number of things. It's not a big deal in and of itself.