Being that she's 19 she might still consider Valentine's Day a really big deal, but if you ask me, birthdays are way more important. It's HER day.
Want to score points? Make her dinner. And maybe give her a gift certificate to a spa she likes? That's what I'd like!
Other ideas that are good: a custom-mix CD as others have suggested, a first edition (or old) copy of one of her favorite classic books (you can write a note inside the cover), movie tickets/concert tickets, bottle of the perfume she wears.
Oh, and I empathize with you...my boyfriend's birthday is two days before Valentine's Day.