1 Corinthians 7:12–16: Unequally Yoked Marriages
First Corinthians 7:12–16 speaks to a household where one spouse has come to faith and the other has not, and it calls for stability, peace, and refusing to treat the unbelieving partner as defiled. It does not address whether a believer may attend a divorced person's wedding.
1 Corinthians 10:27–29 on an Unbeliever's Wedding
Paul permits a believer to accept an unbeliever's invitation and eat without interrogation, because the earth belongs to the Lord. He then adds a limit: when someone names the food as idol offering, love for that person's conscience outweighs the liberty.