Demazure crystal structure for flagged reverse plane partitions

Given a skew shape $\lambda / \mu$ and a flag $\Phi,$ we show that the set of all flagged reverse plane partitions of shape $\lambda / \mu$ and flag $\Phi$ is a disjoint union of Demazure crystals (up to isomorphism). As a result, the flagged dual stable Grothendieck polynomial $g_{\lambda/\mu}(X_\Phi)$ is shown to be key positive.