Counseling. The both of you, and now. There's something driving her to this self destructive behavior. Trust me, I know. BTDT, got the Tee-Shirt.
The thing is shopping and buying release the "pleasure" brain chemicals. So she's unhappy about something, and spends to make herself happy.
And nothing you do will change it. After paying off about $40k in credit card debt the third time, I had had enough. She promised to change, she promised to stop spending and stop using credit cards. Since I didn't pay the bills "The right way", she was going to be in charge of the money. Fine. I went "Cash Basis". I carried no credit cards or debit bcards (can't use what you don't have). They all were supposed to be locked in the file cabinet. She had the check book, so I couldn't be accused of making anything bounce. I packed my own lunches for work each day, unless I was being taken to lunch by a sales rep. If I needed gas money, I had to ask her. I carried $0 on me and would pride myself on how long I go without spending. The only time I had the debit card was on Saturday when I went and bought groceries, from the list she made (many fights over "Why didn't you buy X? "Because it wasn't on the list YOU made out.")
After ~4 years she had opened up three new charge cards, and run up the other two. Total Credit Card debt: Over $85,000. And not a dime of it was mine.
Yeah, Counseling. She has a problem and so do you. If you think you can fix her or change it by putting her on an allowance, you are sadly mistaken. All that will do is generate animosity between the two of you. There's a problem and only by sitting down and talking with a outside, unbiased source will you figure out what it is and then be able to work together to solve it. Any other course of action and you might as well hire attorneys and file for divorce right now.
Good luck.