Well Lou, I do think that she should have some say in what happens to the joint monies--savings, investments, inheritances, etc.

However, I also think she should have her own money--and should be able to spend it however she wishes. If she wants to trade in a perfectly good car for another perfectly good car, let her. What's it to you? Yes, it's wasteful but you are not her. She doesn't have the same values as you do, regarding material things. You are NEVER going to get her to "see the light" in this sense. You're just different.
The best thing to do, imo, is to let her handle it herself. If she wants to waste money on buying and more buying, let her do it alone. Get a job and finance the shopping addiction herself. BUT, she still has to contribute to the household stuff too, 50%.

I think that the shopping bothers you more on a value-system basis rather than on a financial basis. But, the things with that is that there's no way to make HER have the same values as you do. That's really a losing battle, kwim?

It seems like the two of you spend an awful lot of time trying to reshape the others' value system. She wants you to not be a packrat pennypincher and you want her to not be a frivolous shopoholic.
Rather than trying to change the value system, perhaps you can go about changing the specific behaviors that drive the other batty. You can clean out the inventory at a speed that works for the both of you (nope, not ever gonna stop harping on that one! ) and she can handle her shopping by herself, paying attention to your joint budget as well as her solitary spending.
At your cores, she will still be a more material person than you are but perhaps you can learn to live with those differences if you do not feel that you are responsible for keeping the other in line.

Whatcha think.