nisht: Two women is an Issur D’Oraisa of Maaseh Eretz Mitzrayim, which is not Arayos (certainly for a Goy) and therefore is not Assur for non-Jews.
divrei hayamim: This is not Sha’as Hashmad. It’s not L’ha’avir Al Das. It’s L’hana’as Atzman.
By the way, I don’t know how legit this whole conversation is. What’s the Issur of a wedding? The Torah has an Issur of Ma’aseh Biah. I’m not sure why a party celebrating something related to something Assur is Assur for non-Jews.