Actually, I was admired no one in the media backlashed Mariah. Her tribute post was meaningful and though I agree it would have been nice a shoutout to Ariana, I'm glad there was no controversy around it. About Mariah being in the concert, I don't think there would be a point in it, because like someone has said: it was a concert organized by Ariana, and she and Mariah don't know each other..
Even though this is a solidarity event that needs to go above these petty rivalries and the rush of this industry business, I must say that Ariana's public perception must have changed drastically (inevitable promotional gain). Even I felt touched by her performances and by her pain/emotion/struggle conveyed in them . She seemed genuine and meaningful, specially coming from a (former) silly licking-donut spoiled brat.