Help!! Am I wrong for this???!!

My best friend of almost 20 years is getting married in a few months & I’m one of the bridesmaids! She was supposed to get married in 2020 but because of covid and everything it got pushed back a year. It’s been planned since 2019. I just started dating this guy almost 3 months ago and he said he won’t be with me if I go to the wedding without him. If it’s too late for her to add him to her wedding list, I am still going to go. He doesn’t think I should go anywhere without him. Am I wrong for still wanting to go to my best friend of almost 20 years wedding or if I skip it i’ll just look like a horrible friend. What do I do????