A Whole Lot of Nope
All couples have a “This is how we met” story and it’s usually adorable. This soon-to-be-married couple met through a mutual friend and that’s what they put on their wedding website. Nothing unusual there considering lots of people meet through friends. The OP, however, couldn’t believe that they chose to write that because although they met through her, she was dating him at the time.
So yes, he cheated on her with his to-be wife and then added her name on their wedding website like it was completely normal. As she said, we too would very much like to be excluded from this narrative.