How to tell a girl I'm not interested?

So im gonna be a senior in hs next year and a will be junior who was in my Spanish class this past year messaged me on facebook and said she thinks I'm hot. Now, I'm in no way attracted to her physically, both of her face, but mostly she's on the taller/larger side. How can I respond without hurting her feelings? (or this may be a prank. I can't tell...)