I don't hide purchases from her.
It wouldn't work anyhow because she is too smart for that. She'd figure it out.
But I don't ask permission either.
We're not married (yet) so my money isn't OUR money (yet).
I've had this discussion with my GF. She's all for gun ownership but doesn't think I need more than one of anything. She doesn't get the difference between a 10/22 and a CZ-452. To her, if you have a .22 rifle you don't need another one.
This isn't really because she's a woman - it's because she's inexperienced with guns. She really doesn't understand that a Marlin 30-30 does a different job (mostly) than an HK 91. To her, both are rifles that will hit stuff a football field away. If you have one, you don't need the other and you should put the extra money in a savings account.
That usually opens up a whole new conversation about how my latest purchase of $50 worth of ammo provides way more security to me (and her) than the extra few bucks invested in our failing economy would. But I digress...
My GF doesn't really like that I spend money on guns (I'm planning another purchase next week), but at the same time, she realizes that there really aren't any grounds for her to object at this point (again, because it's my money).
Besides, she won't have any complaints at all when she's popping balloons with a stainless 10/22.
Now if/when we do get married, my money becomes OUR money. Then she does have a legitimate say - not about the gun so much as much as a large expenditure. I really wouldn't have any business spending several hundred dollars of OUR money and not getting her input first.
We've already worked out a system to get around that though.
She'll give me an allowance and then take the rest to help with savings, bills, etc. I can save my "allowance" for several months to buy an expensive gun, buy beer, whatever - it's mine.
I have to admit that my GF is kind of the responsible one so realistically, that plan is pretty good for us. She's good with money and will probably be rich someday (if the economy doesn't totally collapse before then).