My boyfriend (29) and I (F24) have been dating for two years now. We've been living together for a year. His family (on his mom's side) absolutely adores me. We've all vacationed together, had holidays together, etc. The one outlier is my bf's sister (26), who from the start of our relationship, never made any effort to get to know me or build a relationship with me.

She still lives with my bf's mom. Whenever we go visit, she makes every effort to avoid seeing and talking to us and if she does come down, she makes an effort to not look me (in particular) in the face. Once, she even pulled my bf aside and began arguing with him that he "just wants to play house" and that our relationship makes her very uncomfortable, giving us no examples of things we do that bother her, other than being an active presence in their mom's life.

My boyfriend's mom told me recently about an argument she and her daughter had about how mom gives my partner and I undivided attention. We take her out to dinner, watch movies with her, go to fairs, and BF's sister is mad that mom can't even maintain a conversation with her fiancé (who is incredibly introverted)

She is getting married next summer (2025). The invite came yesterday and the only person listed as an attendee was my partner. He of course is incredibly shocked by this and does not know what to do about it. I'm angry and hurt. Every effort I have made to try to connect with her hasn't been fruitful.

I want to be supportive of my partner and have been convincing him to go despite my exclusion (they're family after all, I'm not) but I can't help but feel so small and disrespected. What is the best path forward here?