I kept my married name after my divorce as my kids were still at school and I didn't want to have a different surname from them, especially as they were domiciled with me.
True, my older DD is now married and has changed her name but my younger DD hasn't and my DS never will. Moreover, I have spent more than ten years as a divorcee with this surname and just can't be bothered with the hassle and cost of changing everything this far down the line.
I retained Mrs as, though I am no longer, in the eyes of the law, my exH's wife, neither am I, nor have I ever been, my exH's daughter!
If Ms were spoken as, "Mistress" in the same way as, "Mister" is used for the written Mr, then I'd quite happily become a Ms, but I refuse to use a title which, when articulated, sounds unlike any other word in the English language but rather more like a bee with a speech impediment!