It does sound like she's craving the care she had when she was younger although it also sounds like she's starting to take a few liberties.
You don't say how old she is but she does need to try and act her age and live up to the responsibility that having a chlid brings.
Unfortunately she has to be told that, although you love having her around and that you want to be there for her, you have raised your family and you want to have your life back.
Obviously there are probably better ways of saying that kind of thingbut you get my picture.
As for the highchair, she should be cleaining it whether she is at your house or her own. Personally, I would not clean it for her. When she asks why you haven't then you should tell her that it is her responsibility.
recently, my g/f and I had our flat flooded out by the flat upstairs. As a result, we are staying at her parents' house. The first thing we did was to agree on the ground rules. After all, we were in ther place and we should respect their space.