Union tweeted about the experience, calling it "productive."
"We had a lengthy 5-hour, and what I thought to be, productive meeting yesterday. I was able to, again, express my unfiltered truth. I led with transparency and my desire and hope for real change."
An NBC executive echoed Union's assessment, saying "the initial conversation was candid and productive."
Union and Julianne Hough were asked not to return after appearing in Season 14 of the Simon Cowell-created show. Before her firing, Union had complained to others at the show about a "toxic culture" there.
Sources have also said that Union's hairstyles were considered "too black" for the show.
Online supporters have given Union encouragement since a story by Variety first detailed specific incidents of racial insensitivities.
"Thank you for being a voice for change that so many of us desire and long for. It's a difficult time, but know you will always be appreciated and be on the right side of history for making this sacrifice. Be blessed Queen!" wrote @LibQn32.
"You are one of the most vocal and articulate women in the business and I can't think of a better voice than yours to tackle a misogynistic entity as NBC," said @Lottowinner47.