I'm sure I'm not the only one who has issues with their SIL (especially when she's the older and only sister)

Back story: my SIL is 30 (hubby is 28), she's engaged to a multi-millionaire athlete, has 2 kids with him, a huge mansion and is set for life.

Hubby and I have our own business, we work really hard together every single day, we make enough for rent and bills, but aren't rich or anything like that at all. My MIL and FIL absolutely love and adore us together.

Hubby hasn't spoken to her in over 6 months now because of her issues with us and me in particular ( we got married without telling her and he got his grandmothers family ring to propose that I think sister was jealous of or whatever) we are really close with her fiancé and hangout with him and see him a lot.

I want to fix this relationship, I want my husband to have a sister again, I want to be a big family and to be around my nephews but I just am not sure how to go about this.

Hubby says he wants an apology for the way she has treated me and us, I don't care for an apology per se. And she's too hard-headed to reach out. And I don't want to disrespect my husband by reaching out to her first, I believe as brother and sister they need to figure their shit out. I don't want to be in the middle of this and I don't want this family feud

Any advice for me? Please ask more questions if you want to understand the situation better to Help! Thank you!