Seize the Fire is set in August 2382, while Indistinguishable from Magic begins in January 2383. There's time. (For that matter, was the character in question even in StF? The previous TTN book before then was set a year earlier.)
Good question. I don't have the book in front of me but I don't recall her being there. But I'm pretty sure she was mentioned / appeared in the book previously, and the impression in books was that Titan
continued to push outwards, and didn't return to Federation space at any time. Of course, they could have rendezvoused with another ship in that time.
Then again, it's all fiction, so it doesn't really matter.