>>/34572/
Since you mention you age you think that's significant. What if she has reservations about age difference? Sometimes very little difference can cause people to be anxious due to social acceptance. Maybe she's afraid of what her parents would think?
Also it is a possibility she sees you as an "ally" at workplace, a colleague whom she wants to keep content, but don't want to turn the relation into personal.
I know my comment doesn't help, it's just my thought.