How about instead of one of the pride blabing, Vitani runs into Zira, who tells her in a star wars ish like way. No I am your mother, and scar is your father (Right?).
It sounds good, but then we would have to wait for TheLionQueen to come back. Also, there would need to be a reason for Vitani to be out that way in the first place.
All right, that's settled. Now for the argument bit. She goes to Simba afterward, Simba explained. Vitani says she hates him and then runs, interrupted only by Kiara trying to stop her.