Once you have your jeweler friend's information, if it does turn out to be a fake, take the advice to tell your aunt that you think she may have given you one of the copies. If she still doesn't turn over the necklace, you might consider suing her. You'd need some kind of proof that it was meant for you, or for her to agree that, yes, your grandmom meant it for you. I'm sure you don't want to go through that, but it may be the only way to get it.