Cartier captioned her selfie: "I’ve made the decision that Matthew and I are better off staying good friends rather than in a relationship.
"He’s a beautiful guy no doubt about it! Hope you all can respect my decision and support both of us in finding true love," she added.
Around the same time that Cartier shared the news, Matthew wrote a similar message on his own social media.
He wrote: "Moving forward I would just like to let you all know that Cartier has decided that the two of us are better off suited as friends. I respect Cartier & her decision.
"She is truly a beautiful girl and I wish the best for her in the future! Hope you can all support us finding true love," he added.
During their time on the show, Adam broke things off with the 19-year-old as he felt that their relationship had gone stale from lack of things to do inside the villa.
"There's hope for Cartier and Adam," one fan commented on Cartier's post. Another wrote: "We need her to reunite with Adam."
Cartier was left with the heartbreaking decision to send Adam home from Fiji after he decided to break it off with her, saving Matthew instead.
As for Love Island's winning couple, Anna McEvoy and Josh Packham, they are still going strong with plans to move to the Queensland together in the near future.