WWE was advertising Naomi vs. Carmella vs. Mandy Rose vs. Sonya Deville and the winner of that match would have challenged Asuka at Mania.
As noted by Dave Meltzer in the Wrestling Observer Newsletter, Mandy Rose was the person booked to win the match so it would have been Rose challenging Asuka for the title. There was also the backstory of Deville and Rose splitting up that seems to have been forgotten.
Meltzer added that the decision to scrap the match was made because the show is overloaded with matches and McMahon felt like the Asuka/Rose match would have little interest and putting the belt on Flair would make the main event match stronger.