After months of back and forth between the controversial couple, Rihanna and Chris Brown are officially engaged! The “Umbrella” singer, 25, who was photographed with Chris, 23, in Hawaii on Feb. 20 for her birthday celebration, is sporting a simple diamond band on her ring finger, and even uploaded an intimate photo of her and Chris to her Instagram account with the caption, “Like diamonds in the sky.” Her friends, however, aren’t buying it. “Chris still cheats on Rihanna,” says a source. “She just won’t admit it to herself.” Trouble is never far for the couple, who recently avoided each other at a Hollywood nightclub on Valentine’s Day. “He wasn’t into Rihanna that night,” says the pal. “Their relationship is toxic, but she’s over the moon.”