In a case such as this I might have said it depends on the look she gave when she sized you up as you approached, but the thing with women is, they size you up way before you actually approach, so you can't tell what they're actually thinking. If they
do look like they're assessing you when you ask, it's just so they don't seem like creeps that have already considered it.
But to answer your question, she's most likely not lying. If it's your first time asking her, it's not like she's already irritated, and she could have easily said "I'll think about it." or "I'll get back to you on that." or "Gee, I don't know, I have a tight schedule." or avoid the question completely or something! When someone proclaims a sixual orientation, they kinda have to stick to it in front of other people. You say you go there everyday, meaning she sees you everyday meaning she's risking having a boyfriend walk in and kiss her or something if she was lying.
Long story short, improbable. Don't worry, plenty more fish in the sea. Besides, looks aren't everything, right? Right?! Okay, I just lost the crowd with that one. . . :whistling: