When a person constantly contorts their face, licks their lips, constantly works their jaw around, is it a sign that they're addicted to something?

This gal who works at a convenience store here does that. She jut her jaw out, then clenches and unclenches it, work it side ways, and works her mouth around and just….makes odd faces as she’s working. She does it constantly and it’s extremely unattractive! But, I figured maybe she just can’t help it, although she controls the rest of her body just fine. I also thought it might be just a bad habit, but I mentioned her to my daughter who said that kind of behavior is a sign of addiction to something….?