There has been a load of tension between my SIL and my mom for a loooong time, mostly caused by them being so very similar (no wonder my bro fell for her). She caused most of the discord, but to her credit it was because she wasn't about to fall in line like the rest of us do with the understanding that moms will is absolute.
Her daughter (my step niece) passed away suddenly in 2006 so we all decided to let go of the past, but eventually my mother reverted back to her deeply disgruntled disappointment for all the years she lost with the grandkids because of the problems. She doesn't pretend to like my SIL and it's very awkward. Makes holidays with the family something to avoid.

I'm fine with my SIL really, but when she tries to talk to me about how unreasonable my mother is I have to bite my tounge and change the subject because after all, she's my mom.
Who is your FAVORITE in-law and why?