Status of spouse visa after divorce

Hello there.
I have a question please. It is in a way opposite to what most people in the forum have been discussing. My wife has a UK visa based on my visa. She has left me and has gone back to her home country. Unfortunately there is a chance that we may end up getting divorced. I dont think that neither of us want it to happen. But just in case... My common sense tells me that her visa would be invalid once divorced. Am I right in telling that? Secondly, I DO NOT want her to come back to UK as of now. How do I cancel the validity of her current visa?
You now know why my problem is opposite to others. While most of you are trying to get a visa for your spouse, I want to do the opposite. Life is very strange! Anyways, please tell me if you know anything about the above questions.

When does her current visa expire?

How do I cancel the validity of her current visa?

You don't! Forget any thought of you having any sort of veto over your wife's movements, because you don't. All you can do is inform IND of the position and that might alert them if she ever tries to re-enter the UK using that visa.

But before you rush off a letter to IND, are you really sure that is what you want to go? Don't do that unless you are really certain. So you might hold off writing that letter until a divorce actually happens (if indeed it ever does).

Clearly this issue is more relevant the longer is left on her current visa. But suppose there is just one month left on that visa, well you would let that expire and not apply for another visa for her.