Can't use my wife's self deprecating joke against her?
That's rude. Have you ever considered it might be said in jest? Tell me about the situation
I've heard my wife made the joke without considering the emotional damage it can do later on.
If it was a joke, then it's all good and you need to not be so sensitive about it. She may already know the implications about it, so you should just roll with it or else you won't understand her humor.
I don't care. I'm going to use it against her
That a terrible way to act. Don't do this to you wife knowing that the joke was harmless.