In Law Drama

Super long post, sorry!
Important note: my DH has been very supportive and had my back through everything. We are both still confused and hurt but I'm so thankful for him and that he is such a beautiful person.
My sister in law is married to my husband's brother and has known their family/been friends since high school. She is older than I am by about 8 years or so. My DH's entire family is very close-knit and friendly, everything seemed off to an awesome start.
Before our marriage I saw my SIL 3 times, once for a week when we were visiting their hometown. Again, everything seemed awesome.
When we announced our engagement my SIL was a little cold(ish) but I tried not to read into it and everyone else seemed thrilled. My vibes are usually spot on so when she and my husband's brother "couldn't make it" to our wedding, it felt off. I didn't want to assume the worst and know stuff comes up, but there was a definite silence and coldness from them at that point.
The next time I saw them was after our wedding and my DH's whole extended family was there. She treated me horribly for the entire multi-day visit: silence treatment, turning away from me in groups, exiting the room when I would enter. I was shocked, very uncomfortable, and wondered if I did something terrible. She was obvious so my DH also noticed. There were other things going on, I was taken aback, now I wish I would have confronted her right then and there.
She asked to speak to DH alone and said she was acting this way because when he gave her a hug in greeting at the beginning of our visit (after our long drive), that he was as "stiff as a tree" and she was so scared that "things would change".  He was very confused and stood up to her for how rude she was to me and demanded she apologize to me (not to him). I never got a proper apology, it was ongoing silence treatment and weirdness from their side from that point on.
Almost a year later we had happily conceived and shared the good news with everyone. Stilted congratulations from BIL, nothing from SIL. We sadly miscarried. Everyone sent messages and were supportive. Except my SIL. She sent a message to my DH that was clearly, clearly and purposely intended only for him and was worded in a way to offer him and only him support and thoughts.
After we mourned and healed a little, we decided it was time to confront SIL and let her know that her behavior could not continue as it was if she wanted to have a relationship with us and any future children.
She took our firm (but respectful) message and sent it out to the entire family. They then interpreted it as an attack on her from me (although it was written by both DH and I). They act as though I was trying to break up the family or my husband's relationship with his brother.
I now have had silence treatment from that entire side of the family for 6 months. My DH has stood by me and defended us. Now we have a baby on the way again and are so happy but I feel devastated by this family situation. It doesn't feel possible to overcome and I feel sorry for my DH and uncomfortable imagining how things will be after the baby is born. When we announced this pregnancy the response was "meh", one of the sisters didn't say anything for a week.
I just wanted to be part of this otherwise sweet seeming family, and I have never done anything to any of them. 
DH has told me he will speak with them face-to-face before the baby comes (not the mean SIL or BIL but all the rest). I cannot imagine seeing all these people again for the first time right after giving birth, it stresses me the heck out!
I'm also trying to just NOT CARE so much, but I have been feeling truly hurt. 
So what to you think Glow, any thoughts or advice? I'm working to create an emotional distance from this situation, something that does not come naturally to me and I'm struggling. I'm also very confused as to why she has been acting like this in the first place, I was only ever friendly. I also truly feel sad that it seems we have lost all our in-laws' in our life.
PS, I also feel very angry sometimes at ALL of them, not just my SIL.