DO IT! you have nothing to lose, you will learn her level of interest immidiatley, by if she responds, and what she says..I'm embarrassed to admit, I've done this countless times on facebook..but also met several girls off of facebook...just say a hello...and then don't send another message unless she responds, and by all means don't get your hopes up, there are other girls out there, but if she is the love of your life, who knows?