Does she talk a lot? If not - maybe you're the one doing all the talking and your lips get dry. Maybe her desk is by the air vent. Think about those things next time you talk to her. I'm sure you'll figure it out.

even though you say you are not nervous, anxiety comes in many different forms. Excitement is one of them. Often times when in the presence of someone we like the brain releases natural chemicals and hormones which lead to euphoria, excitement, stress and other symptoms. Though you might not have noticeable levels of nervousness or excitement your body is still experiencing some of the side effects such as dry mouth or lips. 1. reason is when you are excited you tend to breath more shallow, this coupled with the release of stress hormones causes the body to halt saliva production. Also your energy levels increase and we tend to talk more quickly and lick our lips or swallow less often, this also contributes to dry mouth and lips. Love/attraction and similar emotions cause a coctail of many hormones to get released into the bloodstream. Often times people become attracted to someone not so much because of the person but because of the high they get from the feeling of being with this person. In contrast often times these relationships dont last long because eventually when in proximity of this same person over time the body ceases to release the chemicals and the high is no longer there, and people attribute this to being no longer exciting, or no longer in love with this person. At this point if you are in love with the feeling of being in love and not in love with qualities of the peron it usually doesn't last. So my advice is enjoy the feeling, suck on a piece of candy or something, it will help promote saliva and also keep your breath fresh in case of a kiss!