if she's in charge, she's in charge. If I want to, I can take all my guns and turn them into the police department...and yes, that would make a bunch of you angry...but there ain't a thing you can do about it, because it's my stuff and it is a FREE country.
If I were you, I'd try to convince her that those are heirlooms and not weapons. Tell her that you would like to see them go to her kids, or to someone in the family, not necessarily you. Be sure that you are getting the point across on this one, that these aren't entitled to YOU but that they are property of the entire family and anyone who is nostalgic should gain access to them. Be sure you remind her that there she has no legal responsibility to those guns if she gives them away, as the government doesn't hold a database of all the serial numbers for 1 (common misconception among non-gunners), and remind her that people kill people, not guns.
If all that fails, tell her you'll pay her for them. Tell her to take them down to the pawn shop to get them 'appraised' if she wants and you'll double that amount. No matter what the pawn shop offers her for those guns, doubling it won't hurt anyone.
Don't be forceful, like I'm being now. Remember, this is your aunt, she owns the firearms, it's her call and no matter what happens she's still kin. Wouldn't hurt to even tell her that. If you go after this like a rabid badger in a henhouse she's going to think that you're up to no good, and she'll destroy them just to clear her conscience.