I don't really like it when I have a girlfriend at a show. I always feel like I have to entertain them before/after and during breaks. I don't like that feeling because I know there is stuff I need to be doing. Getting ready for the show, talking to club managers, talking to press, bloggers, fans, selling merchandise, etc.
It is really important for me to get out there and talk to all the people who came out and thank them, tell them about upcoming shows, band news, etc. When a girlfriend is there you have to give them attention and sit with them.
I guess it's a girl to girl basis though because one of the members of my band has an awesome wife and whenever we play she just sells shirts and cds and enjoys the show and is happy to be sitting alone. that is a special kind of woman for sure.