I'm not medically trained, but the herpes virus you get on your lip is a cold sore. They do hurt, but they are basically a reaction to acidity, as in too little or too much vitamin C. I little baking soda on them can neutralize it; but mostly they just have to heal. They also do not look like pimples.
Pimples on your face are caused by infections in the pores, and the body is pushing the infection to the surface, hence the pussy white "head". A little clearasil could go on them, or the most recent one I've heard is to put a little bit of white pasty toothpaste (as opposed to gel) on them at night. Not all pimples hurt, but big ones DO hurt. Your daughter could be touching that part of her lip regularly, and that could cause a pimple, just like if you rub your nose a whole lot, you'll get pimples on your nose.