How to use "girlfriend" in a sentence

As a result, he had no girlfriend, but he was happy with his books.

Is she my wife? My girlfriend? I think that she is, and I suddenly feel afraid for her

She's been Archer's girlfriend for a long time, and she was alone in the house when it happened! And then, of course, there was Lettice - wanting freedom and money to do as she liked

'Ruin, ruin, ruin! Christ! See, Connie, the funny thing is that I am sure you are the only person who thought it was a disaster to have a sister who was the girlfriend of a big man.'

She talks about a girlfriend but I'm not sure that I know her.'