Will someone please explain something to me?

I'm watching season 5 and why on earth is it made to seem like Carrie is living there in the household with Nathan and Haley? Furthermore, IS she living with Nathan and Carrie? I'm not sure and would love some thoughts. There were a few instantances were I got the impression she is/was- a) when she poured Haley coffee and told her that she'd 'thought she'd go for a swim' b) when she came in and told Haley and Nathan that she was going to bed (in the episode when she kissed Nathan), etc. She's a nanny. I could understand her looking after Jamie in the daytime when Nathan's in the wheelchair and at work but why on earth, when both Nathan and Haley are home in the evening and at night, would she be of any assistance, when both of them are right there with their son?