Don't let restlessness rule your heart. But if you don't love her, then tell her it's time to part and deal with it together. You're not her whole show, but you're important, and you ought not simply run away with Mlle. X, whom you may be using as a wedge to pry yourself free of Mlle. Y and her neediness.
X move away.
If you feel strongly about her in six months, you can go looking for her. All rights reserved.