The Insider.com

This morning, Mariah Carey appeared on Good Morning America -- she opened up about Nick Cannon's health scare, a new PSA she created for the American Heart Association and the passing of her friend Whitney Houston.

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While fighting back tears, she said, "I'm almost incapable of talking about this still ... it's very heavy emotionally.”

Whitney Houston's Funeral - The Tributes

When pressed about her relationship with Whitney, Mariah said, "It was great and I don't think people could ever understand our relationship ... there was always this supposed rivalry in the beginning and then we did the duet and we became friends."

Over the weekend, Mariah was one of the celebrity guests (along with Brandy, Ray J, Dionne Warwick, Clive Davis, Kevin Costner, Alicia Keys and Stevie Wonder) at Houston's funeral in New Jersey. "It was gorgeous," Mariah speaking about the service. "The way she went out and the way family dealt with it, I was very moved. I loved her. We all loved her. May she rest in peace ... her legend's going to go on forever."

The Insider's Complete Whitney Coverage

In her interview, she also unveiled the new American Heart Association PSA she directed. Watch that here.

Finally, Mariah confirmed that Nick is doing much better after his health scare. He has decided to make lifestyle changes -- including quitting his daily morning radio show in L.A. -- that will keep him around for decades!