Girlfriend is 22 (son is 21). Son lives with me, his dad and little brother (6). Son and girlfriend both work part time.
Girlfriend has been staying over 2-3 nights a week since they started seeing each other 2 years ago (we put a limit on it when she once ended up here for a whole week with no sign of going home any time). We have tried to be welcoming to her but are lucky if we get a hello from her, let alone a please or thank you. She has literally sat in my kitchen whilst I've been cooking dinner for everyone (including her!) and has barely spoken two words to me despite me trying to talk to her nicely but as soon as son came into room was whispering and giggling with him.
It feels like she thinks our house is a b&b she stays in with her boyfriend and she doesn't have to bother speaking to the staff.
When we spoke to son about it he said she's shy. But last weekend she was reading a 50 shades of grey style book on our sofa whilst our 6 year old (excellent reader!) was in the room with her. I didn't challenge her at the time as I only googled the title after she'd gone and was shocked. Younger son seems to think she's OK as she deigns to talk to him.
What would you do in this situation? Son doesn't seem to think there's an issue, if anything he'd like her here more! There are no signs of them moving in together any time soon. Not sure on longevity of relationship as its son's first 'proper' relationship.