and back to the topic...... How long have you two been together? If you have been together for a while and she is mature I imagine she can take constructive criticism. If not talk to one of her friends that you both know(trustworthy one) and maybe she can either tell you how to talk to her about it or she can take care of it yourself. I imagine the hair doesn't stop above the lip look at her arms next time.
seeing as you're with her, she may think it doesn't bother you, since you haven't said anything.
although saying something will may her upset but she may make the effort for you if you ask her nicely and don't make a big fuss about it
There's not really any good way to tell her this, you'll have to just be honest. I don't understand how chicks can still walk around with mustaches with all the different hair removal options out there