I agree that when there is an OP firm boundaries need to be set and upheld. Make these boundaries about your principles as a loving H and man, not about your emotions or need to teach her a lesson. That is, if you still love her and want to keep the door open a crack.

M: A really long time.
Crisis: 5 years.
She's still worth it.

Life is never made unbearable by circumstances, but only by lack of meaning and purpose. -Viktor Frankl