Marc Anthony and his much-younger girlfriend, Nadia Ferreira, are engaged.After giving subtle glimpses of her diamond engagement ring all week on social media, the 23-year-old model confirmed Thursday that she and the 53-year-old singer are set to marry.“Engagement party!!!” Ferreira captioned a close-up photo on her Instagram Story of her and Anthony holding hands. She tagged him in the social media upload and added a ring emoji.