Been in a similar situation with my ex.... it's best to just let it go... especially with this much time elapsed. Even something as innocent as holiday cheer might be misconstrued to mean that you are still carrying the torch for her.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen