My girlfriend embarrassed me in front of a lot of our friends, what should I say to her?

We were all sitting around about to smoke a little. My friend pulls out this big pipe he has and someone said "that's like as big as my dick" and then my girlfriend held up a lighter and said "except ____'s is more like this." and suffice to say I got ridiculed. My penis is about 3 or 3.5 inches hard so she was actually sort of right and I don't know if she just didn't realize it was really small and was just sharing but it seems pretty distasteful either way. What should I say to her about this? Is there anything to tell my friends that might make things less embarrassing?