Will She Keep Her Promise?

It all starts as a harmless date to the movies with a 20-year-old underwear model. What happens next? Just ask Jamie Lynn and Bristol.

Miley Cyrus -- wearing what looks like a promise ring -- went to a movie over the weekend with Justin Gaston, without a certain mulleted chaperone in tow.

We don't know if she fell for the yawn-and-grab move.