I think it’s just because he’s not family. It was an industry event, and she knows him through the industry. I don’t remember if they ever mentioned if any of the other main characters were at her actual wedding. I just imagined that her private wedding was family and pre-hollywoo friends only. Especially for Judah, because I don’t think he had nearly as many Hollywoo friends as PC, and he wasn’t even at the industry wedding.