I guess the reason I'm participating in this thread is...
I'm pretty disappointed my last girlfriend and I didn't work out. There were a lot of factors that worked against us and we still remain close friends. It's tough since we broke up so close to the holidays.
I just know I'd be kicking myself and beating myself up constantly if the reason our relationship ended was because I was a complete dumbass and read her text messages. Perhaps your fiance is like a typical women and likes to dramatize things just, you know, to be dramatic?
My sister is happily married with two beautiful young boys who I got to spend the day with...happy as could be. Great husband...his family, mom in particular...basically a bat shit insane lunatic. She gets very annoyed by her and her sister-in-law who is very self-centered. This is something everyone already knows but she plays the part. Does she talk to my mom about it sometimes? Vent about it a little? Sure. That's what you do with in-laws.
Meh. Whatever. I think the OP needs to look at himself in the mirror and correct his actions before he starts a fight with someone he might care about and potentially ruin something that might really be good for him. I think violating someone's privacy is far worse than talking shit about your S.O.'s parents/family.