When I am confronted with this problem, I use several military principals to deal with it. With no small children around to create a safety issue, this works really well:
1) Camouflage: So many look alike at the casual glance. For example, Sistema Colt = Series '70 #1 = Series '70 #2 = Norinco 1911a1. I try to buy new guns that are either duplicates of ones I have, or very, very similar to the untutored eye.
2) Concealment: don't leave them all lying out at any one time.
3) Cover: Keep them in inaccessible places they won't be stumbled upon
4) Dispersion: keep them in multiple stashes so no more than four or five are discovered at a time. DO NOT put more than that in the same range bag or safe.
5) Deception: Be generic when talking about them. "My .30-30." Don't reveal there are three: XTR, pre-64, post-'64 - all the same. This works hand-in-hand with #1.
6) Psy-ops #1: If you ever sell a gun, be sure to mention it. Frequently.
7) Psy-ops #2: Buy her a gun every year or two. Make it a nice one. Let her know you'll take care of it for her.
8) The Nuclear Option/Mutual Assured Destruction: Find out where she hides all her shoes, dresses, and handbags. Hold that back as a trump card if the skirmish goes "hot."
If you use these things carefully, and for years, your life will be much easier. I swear I bet she thinks I only own about 12 guns. If the US Navy had been half as skilled as I am, the Japanese NEVER would have hit Pearl Harbor...