A question out to the females: do you have pimples on your back?

For some odd particular reason, my girlfriend’s been noticing a lot of these hard little protrusions on her back. They’re not really like pimples (because they’re not porous, or filled with liquid), but the size is relatively the same. In a sense, they’re actually kind of like these hardened miniscule-sized grains of rice embedded into her skin. When you pick at them, they kinda just come off, but sometimes they bleed; leave a scab; and then leave a scar (which is bugging the heck out of her). She’s talked to other girls about it, and apparently some of them have it too, and they’ve said that with time it goes away. Does anyone know what these things are? And biologically, how they’re caused, and what might make them go away? Might it have something to do with her diet? Does anyone else know what I’m talking about, and can suggest some type of ointment or cure for it? (By the way, I say this question is out to females, because I’ve asked my guy friends, and it hasn’t happened to any of them. But if you’re a guy and you have some type of insight, help is still much appreciated =] )