So here is the law.
She did not act illegally in the sense that it is no a theft or fraud since her name is ***** ***** account.
It is a clear breach of the agreement and even without the agreement she would owe you the money.
You can and frankly should take her back to court to enforce the agreement and for an order that she pay you back in full and pay interest as well as our legal costs.
In terms of the benefits you are not correct though. She is eligible until you divorce.
In my view, as a senior family lawyer, your best next step is to pay a lawyer to send her a letter threatening a lawsuit and a claim for legal costs.
Then if that doesn't get you the money back you would then bring the application to the court. If you cannot afford a lawyer for that process you can self-represent and if it gets that far you can always post on this site again and I can assist you through the process. I may also be able to suggest ways to get some legal help for free.
For now feel free to reply back with any follow-up questions you may have. If you don't have any then I hope you feel I have earned a 5- star rating but if you don't then please do not hesitate to post back and let me know how I can further assist you. Finally, please understand that even after you rate me I a still here for you and you can post follow-up questions later on if you think of them and there is no further charge for that of course.