When family gets involved, it can really muddy the waters. I wish I had found DB back when our problems really started rearing their ugly head because MWD talks about avoiding that trap. Unfortunately, I had a similar situation to you and just like your W, it seemed to spark the fire that lead us to where we are today. My sister threw a whole gallon of gas on it when she got upset at my W 3 months after W had visited W and BiL about a pair of shorts she had worn during that time while working out.
When you talk with people about your W now, what type of language do you use? When friends and family speak of her, how do they speak of her? One thing I found that helped change things was that I chose to only speak positively of her. If others started to speak negatively about her, I would tell them that I was doing my best to understand what she was going through and that I found talking about all the negative things didn't help. I didn't do this so that it would get back to her that I was doing that, but mostly for my own peace of mind. Re-hashing the things that had happened over and over just felt like picking through the trash.
As a result of that, I found myself feeling less on edge around her and I think she could feel it too because things changed. It wasn't huge and she didn't come running back, but it was a positive step.
Looking forward to more of the story.
M:35 W:31 S: 9 D: 5 M: 11.5 yrs BD: 5/13 W moved out: 7/13