Co-worker told me it was fine to stalk her. What does this mean?

I'm a logical individual so I don't pick up on a persons gesture too well. This lady is quite attractive and I would consider myself the same. Context was pretty much me walking besides her for a few seconds then me saying "sorry not to follow you but I'm heading in pretty much the same direction as you" and she follows with "it's okay you can stalk me if you want". This girl has a boyfriend! This has boggled my mind all night, someone put my brain at ease please!