3rd shoe… in Life Lessons

So I’m having some issues…
My best friend is getting married and wants me to plan and pay for her to have 2 bachelorette parties, 1 with her SIL’s and 1 overnight with me, her and another friend… that’s fine and dandy except she has completely shut me out… only ever hangs out with and talks to the other friend - she doesn’t tell me things, I hear it from the other friend.. whom I don’t much like anymore.. I’ve decided to tell them I won’t be able to do that they can go without me (I wouldn’t feel comfortable with just the 2 of them anyway) I’ve gotten past being sad and now I’m just mad and ready for it to be over with… it also complicated things because she is marrying my cousin and my “other friend” already married a different cousin..
My husband is irritated and thinks I’ve already done too much for her by planning an evening out for us + SILs… he says I need to tell them off and drop out of the wedding.. I couldn’t do that because that is just rude (the wedding is next week)
On the other hand my MIL and SIL treat me rudely, ignores me, won’t talk to me, tells my husband how I hate them… but my husbands advice with them is that I need to just get over it and he won’t say anything to them..
Am I wrong? Should I stand up for myself? Or should I just blow it off and let it all blow over? Please help me.. I am so confused and hurt..