If a cute girl I don't know adds me on facebook, does it mean she's interested?

From time to time a cute girl will add me on facebook that I've never met before in my life. Do girls do that as a way to flirt. Usually if I message them, they don't reply... I don't get it...

Any thoughts from a girls perspective?
If a cute girl I don't know adds me on facebook, does it mean she's interested?
Post Opinion