So everything I'm saying is what I would do and what I/we have done. Only you can determine where your limits have been reached, but IMO if it is a shopping addiction, and she feels bad about it, and you love/care about her, then you could treat it as a health issue and solve it that way (it is solvable!). Now, you have to take care of your own health first but aside from that, remember the commitment you made to care for each other.
We've been in a twenty year marriage and it's better than ever - it's amazing - but we've struggled with addiction issues on both sides and overcome them with the help of each other. I won't say it was easy going and things definitely came to a head and hitting rock bottom and all that stuff. But we came through it stronger together. One of the addictions was gambling so somewhat similar to your situation but there was little hiding since we shared a joint account - same with the other side - no hiding after the fact but still betrayal of trust repeatedly. It was the very worst for about a year, bad for about three years, and going down hill for about five. But again, working through it is the best thing it could've happened.
I'm not saying this is true in your case but IF it is, if your wife is addicted to shopping, then you need to see it has her being a different person than the person you love. If she is able to overcome the addiction ("recover" if you prefer) then things will work out. Look into dealing resources for dealing with addicts, from AA/Al Anon to other resources (whatever works for you, including Google) and you will see that things like relapses and slips are common and it takes multiple efforts for an addict to overcome/recover from their addiction but it is doable and many people have done it. As others have said, only she can help herself. So she has to recognise she's an addict and want help, want to change, etc. It can be done is all I can see. We've not had the monkey on our back for more than a decade, and after a few years, it was as though we had never started (i.e., no cravings, etc.).
We talk about this all the time and it has made us more humble, grateful, etc. Our attitude has been "what does not kill you makes you stronger."
Good luck!
--Ram