Silly pup – she’s being submissive and telling you that you are the top dog in her world, and your friends. Just ignore the behavior, have your friends meet your girl on easy to clean flooring, and it will get better. The more secure your girl feels in herself, the less she will do this. It is a normal behavior modified from wolf behavior; rolling over and exposing your belly is ultimate submission. My Tia used to do this. After years of ignoring it, she felt secure in our home, and she stopped.