Thank you for understanding. I dont talk about it much. Mostly because it is negative and I try to avoid negativity, and partly because I am a little embarrassed about it. Seems like most women have great relationships with their parents...

Good for you trying to make it right and fix things! I think that is important! If they won't reciprocate that and make an effort to make things right, then at least you can rest easy knowing at least you tried.
I cant believe someone would tell your daughter to just forget it and give up on the situation. Especially an in-law! How callous. I know I would also encourage any of my kids' spouses to go and fix things. Life is too short to have negativity and dispute, especially within family.
Your dad was quite right, definitely three sides to every story, and no single person is ever to blame.
I think some people like drama though. Some people seem to thrive on bickering and strife. I have some in-laws that are constantly doing this amongst themselves, and it really seems like they enjoy it in a perverse way...