I wasn't sure where to place my question so I write it here - hopefully it's OK.

It's probably one of many questions I will ask in order to understand my partner and perhaps, with a bit of luck, save our relationship.

Few years ago we used to live in house with other people -family and friends.

First set of people looked like this: my girlfriend, her brother, her "step-cousin" and his friend. All was fine. Then "step-cousin" met a girl and she moved in. My girlfriend was negative about her and hostile. Soon I moved in and problem disappeared. Things were OK.

Then her brother met a girlfriend and she moved in. My girlfriend gave her a very hard time - she was delighted to move out. Now, after few years they are friends but back then it was horrible.

Let me just mention that anytime we had spare room to let out she was always looking for offers from men.

I thought she matured up, we used to live alone as a couple without any other people and things were fine. Few years later we moved in to the house and rent out room to her nephew. Despite her being 12 years older they are good friends.

Her nephew met a girl. She came to stay for few nights with him and then the hell started again. It end up with my girlfriend banning that new friend of her nephew from any visits in our house. I agree that this new girl in our house was socially awkward but I was shocked with the way my girlfriend treated her.

All I know in her teenage she had none but one female friend.

For me it looks like she's very insecure and jealous. I tried to talk to her but she thinks I'm wrong.

Please help me to understand her attitude towards other women - especially those who happen to live with us.