Imagine thinking that your baby is going to be so traumatized by you hiring a babysitter for a few hours that you can’t attend a wedding...like come on. What a dramatic thing for this lady to say. It’s healthy to have a few hours of “adult” time away from the baby.
I’ve also been to a lot of weddings where a baby starts crying right in the middle of the ceremony, I don’t blame OP at ALL for not wanting that (imagine it being memorialized in your wedding video forever). NTA.
This part isn’t my business, but people who make being a parent their entire identity must be so miserable. Like you were a person with likes and dislikes, friends and family, way before you were a parent, does every opportunity to do something fun get thrown out the window because “my baby needs me”? No wonder people get empty nest syndrome, they make everything about their child for like two decades and when the child moves out and grows up they have no idea what to do with themselves.