Mariah said: "I'm almost incapable of talking about this still. It's very heavy emotionally…
"[The service] was gorgeous. Such a class act. The way she went out and the way family dealt with it, I was very moved."
Mariah duetted with Whitney in 1998 on 'When You Believe' and was delighted to have forged a friendship with the 'I Will Always Love You' hitmaker after they were previously seen as rivals.
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Speaking on 'Good Morning America', she added: "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. I saw her toward the end. I loved her. We all loved her… May she rest in peace. "
Watch Mariah Carey & Whitney Houston When You Believe below: