She's entitled to half, as soon as you say you sold the old ones to buy new ones (during marriage) the judge is going to tell you that she's entitled to them.
As was said, get a good lawyer and offer her cash instead of the guns. If she really wants to fuck with you, shell take the guns. If she doesn't care she'll take the cash, just make sure it's in the separation paperwork. I'm sure your lawyer will explain all of this to you.
If I was you I would get a female lawyer that understands how the female mind works. Also have as little contact with your ex as possible or have a friend with you. Don't argue, fight, name call... last thing you need is for her to slap you with a TRO just to fuck you over. The cops will be at your house confiscating your firearms.
Try getting them back after that, most guys end up getting them transferred to an FFL and sold. Or just let them go only to let the state melt them down. Be smart, don't lose your firearms or the ability to own them because of her.