Let's be honest: being single on Valentine's Day blows. Sure, you can wrap yourself in the blanket of "This is a fake holiday manufactured to sell Hallmark cards and heart-shaped boxes of chocolate,"—which is all true—but even the most cynical person will feel pangs of loneliness when they see everyone at the office getting flower deliveries and talk incessantly about their Valentine's Day plans.
This kind of thing can cause your single friends to get panicky. "Maybe I've been too picky," they'll lament to you. You see the look in their eye that says "I just want to be with someone, ANYONE, I have no standards anymore." As her friend, it's your job to head this feeling off, QUICKLY. Just because she feels the urge to couple up doesn't mean she should do it with the first douchebag to approach her at the bar.
Help her through it with this very, very appropos Single on Valentine's Day Card ($5, Emily McDowell Draws). It sets off a huge truth bomb for your friend, gives her some perspective, and ALSO gives her a card to open on Valentine's Day that's not from her mom. Wonderful.