In the beginning of the movie, around 18:52, you can see Nuka bugging Vitani. He breaks the branch and she spins out on the ground a few feet away. When she gets up, look at her eyes. They're a clear blue color. (I noticed this simply because I think her eyes are very pretty here.) Now, fast forward to where Nuka and Vitani are in the elephant graveyard getting the fire. Around 27:56, it will show a close-up of Vitani's face. Look carefully. Now her eyes are brown! By the time she is spying on Kovu at 48:14, they are back to blue. As far as I can see, they remain blue for the rest of the movie.

It can be said that the lioness with him in the elephant graveyard was not Vitanni, but from watching the rest of the movie, it's easy to see that Zira always paired them together to do quests.