Bff Cheating on fiancé

So I’m feeling conflicted. My best friend of a little more then 4 years had been engaged for about a year and I was chosen as the maid of honor. Great, all is going well, I spend a ton of money on the wedding shower (no big deal it was my choice) with almost no help from the bridesmaids. Night before the shower comes, I drive an hour and a half to her house to get the keys and am told she had been taking to another man (cheating on her soon to be hubby) but still wanted to have her wedding shower. At this point, everything had been paid for and prepared and it was almost pointless to not have it but I almost feel like it was wrong of her to play us all including her now ex fiancé and still want to have the shower. Now she’s single, and gets irritated at me for not wanting to go out and drink every few days while I’m at home with my soon to be husband. I guess I’m feeling bad about being distant but i also feel very bad for her ex and I feel heavily disrespected over the fact that I worked and gathered stuff months to make this day as good as possible. What would your reaction be or how would you feel?😩