Rihanna credits Mariah for the reason why she's singing. See Mariah's response.
... but fortunately for Riri, Mariah Carey feels honored. She responded in kind, telling Breakfast Xpress in a new interview: "It's really cool. She's amazing, love her. She's such a great girl and really talented. It's such a huge compliment, so I appreciate that."
We'd appreciate a bit more pep from Mariah, but at the moment is heavily involved with a press run to promote her Vegas run which picked back up Tuesday night.