AITA for not allowing a groomsman a plus one?

I'm getting married to my lovely fiancé soon, and we’re planning an "intimate destination wedding," as stated on our wedding announcements. Our venue can host up to 50 guests, and it’s located about five hours away from each of our hometowns. Needless to say, we are both making sacrifices when it comes to the guest list, and while we’ve both accepted the intimate nature of this wedding, we’re at odds over one particular guest.

One of my fiancé’s groomsmen (let’s call him Ron) has been dating a girl for 10 years (let’s call her Sal). Since my fiancé first started introducing me to Sal, she’s disliked me. We’ve attended parties together. I’ve tried to be friendly, but she actively ignores me. I remember once trying to make small talk by saying, “Hey, we have the same scrunchie!” and she replied with, “Yeah… I heard.” (I’m still not sure what that meant.) I’ve always tried to remain cordial. Fast forward to our engagement party—we invited 80 people. My family flew in from out of town to attend, and Ron and Sal were invited. Ron immediately took Sal to the backyard to watch his favorite team’s game instead of socializing with everyone else (though he did bring beers, which was nice). Ron greeted me and met my family, but Sal ignored me. That’s fine; I understand she’s not a fan. What really bothered me, though, was that at the end of the night when everyone was hugging, Sal hugged my fiancé. When I opened my arms to give her a hug, she pulled her arms into her chest and said, “I’m so cold,” essentially rejecting my hug. She then walked behind me to hug my fiancé’s parents and thank them for the evening. I’ve heard from Ron and mutual friends that Sal has no intention of accepting me. She’s actively negative toward me and our relationship and doesn’t like when Ron hangs out with us.

Am I the asshole for not wanting to invite her to our wedding? My fiancé says if I don’t invite Sal, it’s likely Ron won’t come to the wedding, though he was excited to be part of the wedding as a groomsman. He also believes Ron will end their friendship entirely if we don’t invite Sal. I understand my fiancé doesn’t want to lose his friend, and I respect that. I suggested he talk to Ron separately (or even explain things directly to Sal), but my fiancé thinks Ron will be too hurt to understand our side and will walk away from the friendship.

I just don’t want anyone with negative feelings toward me at my wedding, especially since it’s such an intimate event. It would be awkward to have Sal sitting next to my grandpa or childhood best friend, and I know I’d be anxious about it throughout the weekend. I haven’t given anyone else who is unmarried a plus one, not even my bridesmaid who is flying in from England or my cousin (who’s girlfriend I only just met at Christmas). If I don’t give Ron a plus one, I could use that invitation for someone else (my aunt, a high school friend, etc.).