Is it permitted for a Muslim to attend a wedding where a Muslim woman marries a non-Muslim man? Does attending such a marriage indicate support for the wedding?
Well done, you inquired either a nice or significant matter. As you yourself mentioned in the last part of your question(s), doing this practice (attending a Muslim woman marries a non-Muslim man) would directly or indirectly indicate that you (the Muslim who attends in the mentioned wedding) is supporting and confirming the practice of that Muslim woman. Then Moslems should observe the mentioned issue and do not attend in such wedding.