We don't know how long she was married to her exH.
We do know the cheating occurred over 10 years ago, so any character growth she has developed was not "overnight".
Okay - no matter how long - she still made it right in her head to go ahead and do it.....
and yes the cheating occurred over 10 years ago - BUT, once again, my experience is once someone has crossed the line, it is easier to do it again. Just my experience....
Others may disagree - I counselled people who had rouble with the law and they told me it is so much easier to cross the line once you have crossed it in the past and even after they "change" they find themselves often tempted to do it again.
Thus the concern of the poster and my concern.
Funny story - I was married to my wife for over 25 years and I used to say to her when we were married that if I ever dated again I would be such a different person and behave so differently because I had all this insight on relationships and did all this growing while married...yet when I started dating - funny things started to happen that were remarkably similar to when I was dating over 25 years ago......coincidence? I do not think so....
point being - we think we have changed but when push comes to shove underneath it all we are the same.
Perhaps she could change her behaviour but underneath it she thought the grass would be greener (a character issue) and I believe the poster has a justified and normal right to be concerned.
Why do most women always ask the man they are with if they ever cheated on former girlfriends (mine always did) - to see the person's character.....just my .02