In the end of the mission the timeship only beams the alternative you off the Enterprise-C, saying that they can't risk you effecting the timeline, BUT there is another individual from that alternate 2409 on the Enterprise who seems to make the trip back to Narendra III in the past as the captain of the timeship leaves her on board the Ambassador-class starship:
Just imagine the possible consequences
Walker probably picked her up and did the same thing to her as he did to you. That, or there are two T'naes just like there are (or were) two Tasha Yars.
"With the first link, the chain is forged. The first speech censured ... the first thought forbidden ... the first freedom denied ... chains us all irrevocably."