"Mom, do you really wish Dad could wake up now? If you truly do, if there's a shred of guilt towards him inside you, then please stay by his side from now on, and never think about anyone else. Don't mention these matters in front of him again.
You should know that for a man, having his wife hold another man in her heart is an immense shame, yet he was willing to let go of all that shame just to be with you. This proves that deep down, he truly loves you. Why can't you just let go of your prejudices for his sake? You always do as you please, but you forget how much pain your actions have brought to those behind you.