If you've got ADHD, might she have the same thing (but with a different set of most annoying symptoms - obliviousness to someone else being too busy to chat could well be one)? Now is a good time for her to persue a diagnosis, if she doesn't already have one and to take a look at Access to Work funding for when she finds a job.
Leaving university can be a difficult time - lots of support structures are lost / change and money can be tight. It's worth her considering - how to stay in touch with friends / finding a counsellor / considering if she's depressed and seeing a GP.
For you, I think routine tweaking is worth trying - maybe incorporate a walk or a bike ride or a car journey into some days of the week, so you have guaranteed alone time. No, it's not the same as alone time in your house, but whilst its summery, it's maybe worth a try.
One of the things I've thought about since the first lockdown is about how to manage many people in the same small space and one obvious thing to try is for each member of the household to go out for a walk/bike ride/car trip alone at different times of the day. Would she be up for a routine that incorporates going out at a regular time some days of the week (to the library / a shop / just for a walk)? Does she need help creating a routine for herself? You're probably not best placed to help, but this is the sort of thing a ADHD mentor type person could help with. Does she have local friends? Would she be interested in organised activities locally eg. volunteering for a charity / joining a book club or similar?
www.ukaan.org/support-groups might help - if there are any groups close to you for you attend together or encourage her to attend elements of the groups aimed at partners/relatives, so she can speak with other people who live with people who have specific needs for quiet in order to focus etc.
I'd be explicit that you need to be able to batch cook alone for disability reasons [and maybe money saving reasons] but offer her specific times when you're free for conversation [remember one of the other ADHD things being rejection sensitive dysphoira]. An alternative is the two of you learn how to batch cook together effectively.
Think about things you can do to improve the house to reduce the sound carrying - this might be as simple as hanging curtains against some of the walls or a complex building project. I suppose noise cancelling headphones are worth looking at for both of you. Making sure there's some space at home each of you can call your own is important. I think it's worth planning for your daughter to be living with you for some years, given the state of the economy - it's worth considering moving house and/or building work to make more space if you own the house. A shed / summer house / other outbuilding type thing in the garden might help.