I'm sorry, I think you've been given a really hard time here OP. I grew up with mum on her own, cleaning houses to make ends meet, so I know it's tough.
We have two adult children plus one partner at home and we don't ask them for money, but that's because at this stage of our life, we can afford not to.
I'm sure that your daughter is well aware of the situation and must enjoy the perks of washing and cooking.
The only thing I'd suggest is, if you can manage, without telling her, quietly save 10% of what she's giving you and gift that to her when she does eventually move out.
At this point, I'm more concerned about you. You're nowhere near retirement yet, but renting in retirement is really difficult. I'm in a country where the system is different, but have a little knowledge about your system. Are you able to pay for any catch-up years of National Insurance? Obviously, you don't need to answer these questions here online, but do think about your answers and plans.
You say your daughter will have around $1200 left over each month, does that mean you will have the same? If so, now is the time to work on both a retirement plan and perhaps save a deposit for a small place of your own. Twenty years will go faster than you know, but at the same time, it's also enough time to make a big change in how your retirement will look. Maybe get into the money and retirement pages here. If you were in the same country as me, I'd know which books to recommend, but the local library will be able to help you. There will be Facebook groups and Instagram pages that focus on retirement in the UK. Maybe ask for recommendations in those pages on EB.
For me, I'm much closer to retirement, but in the last 5 years, I've learnt so much and definitely improved my situation, but wow, I wish I knew 15 years ago what I know now.
I follow four different finance people on Insta, a very young one, her info is aimed at the younger set, but I find it interesting and pass on some ideas to my kids. I follow a guy who focusses mainly on wealth building in the 30's and 40s and I follow two who are really looking at the pointy end of retirement.
I know you probably haven't had much spare time in the last 20 years, but now is time to really make a plan, while you've got 20 years to put it into effect. Getting started can be daunting, but honestly, the sooner you get started, the sooner you'll see why it's important to get started.
Wishing you all the very best!