Should i let go

I recently got engaged a week ago on my 5 year anniversary it was absolutely beautiful. I've know my fiance 15 years but been dating 5 years and now engaged my sister in law is 7 months pregnant about to be 9 pregnant she had her time celebrate and show off her being pregnant but nobody seems care about us every time we are around her she always brings us her pregnancy always gotta make everything about her and just steals our thunder idk what to do.