Oooh Heracles - what's bad time - sounds like fun... do you need to bring keys??
LadyD - YANU to want your own time/space/friends, but it's difficult.
You have chosen to have another adult living in your house, for your convenience. She is a person, living there, for now it is her home - not just her work place.
It's hard work living in someone elses house; not knowing if you are being more polite to stay and chat or more polite to say 'Hi' and run. Not knowing if they think you are there too much or not joining in enough. Just not knowing what is expected and acceptable. It's pretty shit at times to be honest.
It's really quite horrible to say she lacks the emotional intelligence to work this out for herself - you don't actually know what's appropriate and what isn't, you and your DH can't agree - yet you feel it's OK to be rude about her 'take' on it.
She is living in your house, the onus is on you to make her feel comfortable.
If you were to do as has been suggested and say to her that the adults will be eating together, she'd be well within her rights to tell you to piss off - she's 21 not 12. I can't believe some people have actually said that... beggars belief.
However, you and your DH disagree on the level on involvement/inclusion, so that is something you need to sort out.
Do you spend significantly more time with her than he does during the week?
You need to have a really good talk with him about this - you don't want to be rowing over it!
I suggest that once you have talked to DH and agreed what level of inclusion you will be inviting her to have, that you have a talk to her and tell her what that is - nicely, without being patronising.
Also - if you and your friends are having brunch/dinner - does this mean she doesn't have access to the kitchen?
I can see it from both sides, as I said, it can be really shit living in someone elses house (even when you like them) and it can be shit having someone else there all the time - even when you need & like them!
You need a house with an annex 