Maybe she is turned off my your insecurity over this minor issue.

This sounds like one of those things that spirals out of control. Like when a guy has performance anxiety, which leads to a weak erection, which leads to more anxiety and more problems. Maybe she had the dryness once or twice, noticed your concern, and now she is nervous enough to have a problem all the time. And I say "problem" becasue YOU think it is a problem --- it's not really much of a problem, just get over it, use some lube, and enjoy it.