Would it be weird if I friend this girl on Facebook?

So thing is we never had a conversation in person. At my friends house I've known him and his sister for a long time, my other friend had gone up and went up to my other friends sisters friend and had said we all thought she was attractive. Turns out she found me attractive too and not the other guys but it's been awkward ever since but I kinda want to add her on Facebook and maybe chat her and get to know her to smoothen things up. Or would that be weird? What should I do?