Should I ask her on a date or send a message first?

simply put, there's this girl I know, we're both 15, and I really like her. She's given me a few "signs" such as long eye contact, and resting her head on a seat smiling at me, as well as talking to me at least once every opportunity she gets. I know these are not 100%sure signs The question is: As valentine's day is coming up, should I simply send her a happy valentine's message on face book (we're in our holidays so I don't see her at school) or should I ask her if she wants to meet up on that day (through Facebook as well)? Obviously the second one is more risky so I really want some help on this.Yes, we have been talking for quite a bit now. Adding to that, one night she started asking about my family and stuff. When I asked her what she would be doing during this holiday, she replied that on valentine's day she'd probably be watching a sad film. Is this something I should have picked up on?