Especially when the school probably has real social distancing policies in place and that wedding does not.
I don't think missing your brother's wedding is a big deal when you have 10 of them plus a cousin your parents are raising and 8 sisters. With as big as the family is, it's inevitable that not everyone will make every wedding. They even said that at one of the weddings. I can't remember if it was Jill's or Jessa's.
She might have been there, but skipping the out-of-state, COVID spreading, teenage wedding sound likes okay to me.