I just want to second MerryH's advice. Spot on solid.
Do some low-level flirting. If she doesn't respond, lay off and she'll think you were either being silly or lonely and are now over it.
If she responds, it may just be her being friendly or sharing a mutual ego-boost (hey - we all need it now and then), and the way to test this is to ask for a DATE.
Regardless, keep treating her with all the respect you give her now as a friend and don't push her further than she wants to go (okay - test the boundaries a little on occasion, but be ready to back down quick). Do those two things and your friendship will remain solid, regardless of where either of your feelings takes you two.
-PP