Something like this would eat at me forever. I'd have to confront.. but the way I would do it would be sort of like benefit of the doubt way as much as possible. Tell your aunt that you're concerned that she might have been ripped off because it's a fake, ask her if she still has receipts so maybe she could try to get her money back etc. etc. - so basically, not putting fault on her so much as "concern" for her being "tricked" into buying/gifting a fake.
Good luck, whatever you choose to do !
Good luck, whatever you choose to do !