Husband’s crazy SIL wants to “help” (LONG)

Some background: My husband and I married in late 2017. We asked all of our siblings (his 3 brothers/wives and my two sisters) to be part of the wedding party. I was thinking of including his oldest niece and nephew (children of his oldest brother) to be the ring bearer and flower girl in early 2017 when I started planning. Told my MIL I was having this idea and she told my husband’s brother. I ended up NOT having a flower girl and ring bearer as we chose to go the traditional route in our culture (we’re Mexican-American and catholic so we had “sponsors” for all of the rituals). After my MIL told (blabbed to, really) them about the idea and I never mentioned it to them, they threw like 30 fits in the summer and blew up at my husband for not including the children, said “things” about me so I cut his SIL (let’s call her Bertha) out of the wedding party that same day (you don’t call me a bitch and stay in my party). They never showed up to the ceremony or the reception and didn’t speak to my husband for a year. My husband never kicked his brother out of the party and they were still invited to the ceremony and reception. Again, this is all because I thought of an idea for the ceremony and chose not to go through with it WITHOUT ever even telling them I had the idea.

I’m 29 weeks pregnant and my mother, MIL, and sister are planning my shower. We handed out invites yesterday and as soon as we did, my husband’s oldest brother said he and his wife want to help with providing the candy bar at the shower. I’m iffy because Bertha is crazy as hell (read above). When my husband’s 2nd oldest brother’s wife was pregnant, my MIL was the one who threw her shower for her and asked me and her sisters for help (never Bertha). Her sisters and I helped out lots and then Bertha jumped in and high jacked the planning. We couldn’t contribute time, ideas, or money anymore because Bertha decided she wanted to take care of it all. The day of the shower came and Bertha pulled my husband’s SIL’s sisters to the side and talked crap to them about not helping her plan. 🤷🏽‍♀️

I don’t want this crazy lady to be involved in any way, shape, or form because they couldn’t even support my husband when we were getting married. They talked shit about me to my in-laws before they came around and started talking to my husband again. She’s bonkers and narcissistic.

HOW do I get rid of her “kind gesture”? I wasn’t even having a candy bar at my shower. If I say, “thanks, but no thanks” they’re going to have a shitty fit. If I let them contribute, they’re going to hold it over me and my husband’s head (they’ll find a way to bring it up in the future).