Why should you not go out tonight with your girlfriend and her friends?
If her friends are girls and you go out with them and your
girlfriend theres a chance that they will flirt with u. It will end
very bad. Going out with just your girlfriend is much better, or if
she really wants you to go with her and her friends, ask her if you
can bring some of your friends, that way your girlfriends friends
have other guys to flirt with, rather than with you.