If you listen to jfalcon504 (who must be a guy) she is out of your life forever! Some men just have no clue.
Tell her you would love to see her after hours and that when you are at work, It's work only, no funny stuff.
By letting her know you are keeping work and play separate she will respect you more and realize you are not just after one thing.
Explain you understand her feelings and that you would never put her in an awkward situation.
Kindness and honesty work. Roses and a picnic don't hurt either!