I don't recall ever seeing the interview where Madonna said she'd rather kill herself than be Mariah Carey. But she supposedly said a few other things about her in the mid-90s that were not at all complimentary. I think Madonna was still reeling from the backlash and found herself resenting art she didn't consider as challenging performing so much better. She admits that she said and did a lot of things during this time that came from a place of deep anger. I'm sure at this point she's come to respect Mariah as another legend who's survived all of the industry trap doors.

She did say in 2008 that she liked Mariah's record, so there's that.