How do I cut off a friend who shows no interest in my life?

DEAR ABBY: I have a casual acquaintance, “Stacy,” who long ago moved to a different part of the country and sends me a message every couple of months. She’s not a friend I would ever think to visit or even call on the phone, and she apparently feels the same.

Stacy writes that she “wants to keep in touch,” yet her messages contain nothing more than a greeting followed by a perfunctory response, like “been busy,” when I ask what she’s been up to.