Here are some of the ways they might reach out to you.
She came back as a ghost in Ghost World to help Stefan, who had turned off his humanity and returned to his ripper behavior.
Also, she was one of the ghosts who appeared in Mystic Falls when Bonnie dropped the veil in The Walking Dead and Graduation.
Lexi met Elena Gilbert briefly before she died and gave her some relationship advice, encouraging her to give Stefan a chance.
Elena thought of Lexi as a friend after they talked, realizing how much she cared about Stefan.
If you look closely, you'll find traces of them through history. After a thousand years, things can get complicated.