That is YOUR fault for not protecting YOUR money.
Legally...you can't do a damned thing about it.
Your right, "for now" but when the divorce is filed OP can easily get statements from the bank showing her emptying the account and she will be forced into dividing it up. That's assuming she sticks around though. If a couple gets a divorce ether's 401K account is usually divided 50/50, you could go to your 401K plan-holder and close the account and dump it into a savings account in your name only but in court it's not going to matter, it will be divided. I do agree with you in the separate accounts though, keeps arguments to a minimum IMO..