AITAH for refusing to attend pre-marriage therapy with my future SIL?

AITAH for refusing to attend pre-marriage therapy with my future SIL?

Im on a throwaway because I have friends on my main and contribute to other subs.

I know/think this is going to sound crazy. I’m here to get some outside perspective because I don’t know if I’m crazy or this woman is crazy.

So my brother Liam (32) is engaged to his girlfriend of nearly three years Casey (31). We (parents and other siblings) were all happy for Liam, he adores her. My parents offered a substantial amount to contribute to the wedding. Well wishes all round, to be clear.

But two weeks ago, we all get added to a group chat by Casey, and receive a long message saying she wants to schedule 8-12 sessions of pre-marital counselling with our whole family. She said it was “to share her history” with us and “make sure we were all prepared to accept her into the family, with a full understanding of her needs”. These are direct quotes. Needless to say our family group chat lit up immediately because what? Liam later explained to my parents that Casey sees a therapist because of her issues stemming from growing up in the foster care system, and she had brought him into a few sessions when they started getting serious to help communicate her feelings. He said she now wanted to do the same because she wanted to be a full member of the family, as accepted as another sibling.

I told my mom I’m not doing it. I think this is completely nuts. I’ve made accommodations for Casey – I didn’t say anything when she left rotting food in my house, I went to lunch with her when she bugged me incessantly two weeks after giving birth, I’ve listened to her trauma dumping. Because she makes my brother happy. But this is too much. People get married every day. She’s not special. We don’t all have to take classes on how to treat her just because she’s marrying our relative. That’s crazy, right?

But apparently my parents feel too guilty not to go, and now because I said I’m not, my other two siblings have said they won’t, and it’s a mutiny. Liam is mad. But am I wrong? I think this sets a terrible precedent that Casey needs to be coddled and prioritised by the whole family. We’re not marrying her. I don’t consent to all this information about her or to making her the centre of the family. But now I’m being painted as uncaring and rigid for not agreeing to hear her out.

Am I completely losing it here? Is this a thing people do now? My husband thinks Casey is unhinged and fought with Liam over this but like I said my parents think I’m being harsh.