A bitch says woof & walks around on 4 legs.
A woman says lots of things (in some cases you'd wish she didn't, especially when you're trying to watch football, but still...

) & walks around on 2 legs. This applies to girls who work in porn as well.
If you want to call your girlfriend/wife a bitch while fucking her & she agrees with it or if you're getting paid to call her a bitch at least 15 times during a movie & the girl in question has read the script as well, it's ok, but if you start calling a total stranger a bitch then you go too far.