SIL's Birthday vs Death in the Family

Alright so my MIL and SIL have some weird codependent/narcissistic/emotionally incestuous relationship and everyone has to accept it. Everything is about them 100% of the time. In MY hospital room following my C-section, everyone talked about my SIL's upcoming surgery. At Christmas, my in-laws TOASTED to how brave my SIL is... And no word of congratulations on my husband and I on our first year as parents, or two my BIL who has lost 100+ pounds following weight loss surgery. It's been 5 years of this bullshit where no one else can be as sad, disadvantaged, wronged, injured, sick, whatever as they are. It's my SIL's birthday on Friday but my MIL asked if my husband and I (and our son, who they really want to see) would go to lunch. Here's the problem: my beloved uncle and godfather passed away on Friday after a 5 month battle with pancreatic cancer. My husband has to travel for work and won't be home for the funeral on Monday. I asked him if we could just stay home for the weekend so I can have his support in grieving and so I can have some time to be sad without also having to be "Mom" or put on an act that everything is fine. I said we could buy her a birthday present to wish her a happy birthday but say "Sorry, we can't make it to lunch". He won't stay home unless we can tell them why we aren't going. That shouldn't be a problem, right? Except for in 2022, my grandpa died suddenly and unexpectedly the week of Christmas. It was devastating to my family and came after a doctor's appointment where he was told "I'd say you have 10 more years to live!" I made the rounds to my husband's family because it was Christmas, but my MIL's reaction could be accurately summed up by "That's sad. Anyway..." As if my goldfish died. So I don't want to open myself up to her not giving a flying fuck about this loss either. I'm devastated. But my therapist recommended I have to make some kind of compromise and here are my options: - don't go to lunch but tell them why - just husband goes to lunch but tells them why I'm not there so he isn't a "liar" - I go to lunch and medicate myself to get through it, but I don't have to share a vulnerable moment in my life with them. I'm sure I'll just go to lunch and have AirPods in so I can't hear them bitch and moan about every minor inconvenience in their lives. But I'm at my limit with his family and I wish he would just support me 🤷🏼‍♀️