I bought a fat chick from work lunch when we were at a training seminar.....?

(all you can eat buffet) I thought I was just being a nice guy, now she is obsessed/stalking me. She insinuates that we are dating. What can I do? I have no attraction to her at all, she's just a nice person I work with. My friend says fat chicks are like stray cats, feed them once and they will never leave. Should I report her to my boss?