Can i ask a girl out on facebook (I know her)[VERY Long 878 characters]?

so i like this girl that i have hung out with for about 3 years and i want to ask her out before i change my mind (i am vey unfocused) i am probably about 200 miles away currently and i do not have access to a phone. i was wondering, well, if i should ask her out on facebook, i am 90% sure that she would say yes if i did it at school, what would be the percentage decrease if i did it on facebook (this is how i visualize stuff, I'm a math geek so i would understand it better in number form). sorry for such a long explanation but i figured to get an accurate answer i would need to include every detail. if appearence is a concer i would say we are on the same level. Thx to anyone that helps me.(i wont see her for about 3 months and that depends if i have any classes with her im not taking any advanced and she is so??????) once again thank you to anybody that helps