Is it possible that working crime scenes in New York again will make her want to stay?
She clarified to Sherlock in the premiere that not being 100% happy in London didn’t mean that she wants to leave London, but circumstances have changed.
Sherlock gave up his whole life in New York to protect Watson, although the Season 7 premiere made it clear that he’s actually quite happy in London, and not just because he gets to eat ice cream at 10 a.m. with Kitty’s son.