Ugh. This is so hard, isn't it? My 2 oldest kids found out about the A 6 months before me, so my Dday was immediately complicated because they had already been venting to friends, etc. We had no choice but to tell our extended families, as they needed to know what was up with our kids. A huge mess. We live in a large city, yet our community makes it feel like a small town... so we soon became the subject of much gossip. The A shocked everyone else about as much as it shocked me.
It's really hard to deal with family and friends during this process. I know that they feel anger on my behalf and feel the need to let that be known. People really don't know how to handle these situations as concerned bystanders. I love the saying that infidelity is a trauma where no one brings casseroles. Those who haven't experienced it have NO idea the rollercoaster of emotions we experience as BS (and even WS).
It helps me to remember that they mean well and only want what is best for me and our family. They don't want to see anymore hurt inflicted. And they have NO idea what to say or do. I've had people say the most unbelievable things -- family, supportive friends, and even acquaintances who have no right to say squat. I'm a very private person and it was VERY hard for me to accept that I was the subject of talk and gossip and that we are perpetually being "watched". It sucks.
At some point, though, I learned to accept this and deal with it. What matters is what I think and what I want and what we are doing to repair our M. The others are irrelevant. Except for my kids. They are profoundly affected and want different outcomes. Their opinions DO matter to me and make attempting R extra difficult. I still haven't reached the win-win scenario I desperately hope for.
It sounds like your SIL is struggling with how to balance her emotions and provide you with the proper support. I give her credit for trying to adjust. I know your WH would just like to escape it all... but the reality is that that is not the answer. He, unfortunately, has to face the music. He made choices and those choices have consequences. It sucks, but it is real life. I hope he can take on the mantra that a person should not be judged for the mistakes they make, but how hard they work to change and grow and make reparations for those poor choices. It takes courage and strength to get to that point. It's why A's flourish in the dark, but rarely can sustain the harsh light of reality.
I know it's hard, ladycody. I've been there and am still dealing with the fallout. I know I've grown stronger through it though. I wish you all the strength and resilience you need to push through this. Sorry you find yourself in this position. None of us deserve it. Hang in there!