-Do you have any mutual friends?
-Does it seem like she may like you for more than friends?
-Do you only talk on facebook and text or do you see her in person?
The only advice I can give you is not to let a good thing get away some of the best relationships were built on friendship first what you both will have to do is make up your mind that you won't let a relationship mess up you friendship. What I would do is sit down and think about what you want to say and then type it in an email and explain to her that you don't want to lose her friendship and will understand if she doesn't want to date you. She may not be ready to take that next step with you yet so be patient. You are going to have to make it a point to make more time for each other so that you can connect on a higher level than friendship and facebook friends. Try to set up a date make it lunch or a movie but make her think she is going as your friend, tell her how beautiful she is even if she only has on jeans, also make eye contact when looking at her this may tell her to do subtle things to show you she likes you like flipping her hair or smiling when you look at her, then if things go well, then your aim here is simply to arrange a second date but on a more serious level. Don't get involved in saying how attractive you think she is if you have had only polite feedback simply say: "You enjoyed her company and want to see her again" It may take several dates as friends before it comes to the point where you can tell her how you feel.