As most us know, Mariah was hired to be one of Brenda K Starr's backup singers back in the 80s. The two became friends and when Brenda took Mariah to a party, she famously handed Mariah's demo tape to Tommy Mottola (her future boss and husband), and the rest is history. Mariah gave thanks to Brenda throughout the 90s and even covered Brenda's hit song "I Still Believe", but do you think Brenda is wildly jealous of Mariah? She practically handed Mariah the career that she herself wanted.
I don't think so, I mean if she really is a friend she will be proud. And the fact that she gave the tape to Tommy meant that she may not be the jealous type.