Think that’s a sticky situation? Hows this: You get invited to a mixed marriage”
I had to deal with that when my husband’s ONLY niece married a goy. We did not go. it took a long time before the breach was healed because we “disrespected” them (their words). But we could not compromiseon this.
I see no problem with inviting a non-Jew to a wedding, especially if they are co-workers and others in the office are invited. Our non-Jewish guests dressed very tzniusdikly, and really enjoyed watching the proceedings. In fact, at one simcha at which I was a guest, they were the only ones who gave tzedaka to the man was coming around collecting during the chuppah (a practice which offends me greatly, btw, and I as a baalas simcha would far prefer to give tzedaka to someone in a nice amount and have him NOT bother my guests and disrupt a wedding).