I understand that it technically isn't your business from what OnlyTheTruth has said - but it is a legitimate question. If I were in that position I would be curious as well.
I am not sure it is a relapse of sobriety but as lpnangel said...percocet for a headache...a liiiiitle much - unless she suffers from extreme migrains and she was prescribed it...which you said she wasn't.
It's a tricky question actually - I am curious what others will say.