(written from a Production point of view)
According to "It's Federation Day!", a newspaper article created as background material for Star Trek Generations, Ambassador T'Jan was the Vulcan representative at the Federation Charter signing ceremony on October 11, 2161. The clipping quoted her as saying, at the conference, "Following the end of your world's war with the unseen Romulan enemy, such a union as we create here today is the most logical course of action any of our peoples can take."
Although the article containing this information was present within the Picard family album during the filming of Generations, neither the character of T'Jan nor the rest of the article is considered canon, because the article was never seen on-screen.