Meeting Gay Sister’s Fiancée

This is a question you must decide, but I would consider so out of love for your sister and thus for her eternal salvation—and for her friend’s as well. With God’s blessing, you may be able to make a positive impact on your sister over time.

Consider bringing a friend or another family member with you. You can affirm that your sister has a genuine friendship and sisterly love for her friend but that attempting to express that love sexually is an invalid expression of that love—indeed, a betrayal of it.

Obviously, you could not attend their so-called “wedding.” For more on that, see this previous answer. God bless you in striving to witness the truth in love to your sister.