There is no way to know for certain what actually occured between Michael and Tatiana. However, we do know for sure that Tatiana took it upon herself to change the routine a little bit and actually kissed Michael Jackson during the performance, and that she was subsequently fired by Frank Dileo for doing so. We don't know for sure whether it was Michael's wish to fire her or not, but considering she reportedly waited outside of his trailer for hours and he wouldn't speak to her, we can assume he simply didn't want a relationship with her. I also think that if Michael wanted her to remain on the tour, he easily could have made it happen. He was the boss, not Frank Dileo. I think she was just too starstruck - remember, she was getting close to the biggest young heartthrob of that era, of course she'd want to hold onto that. However, Michael has made it clear several times that he isn't comfortable around people who are too starstruck and who are also playing for his attentions. He wanted people in his life who he could be certain weren't interested in him for fame or money.