I've been in this situation OP and now I have more shit in this house than I thought would fit! It will get better.
DD and I shared an air bed when we moved in, she was 13 as well so not little, but it was better than the floor. We had a microwave and a kettle. And for the first two weeks I used a jar lid for a plug in the bath and sink because it didn't even have plug.
It was really basic but it's what you need to get through to get the security you don't have in private rent.
You said you work - my HA put me in touch with a charity that helps people in my job (guess from the un 🤣) and they paid for 3 carpets, a cooker and a bed. I cried when I opened the letter. I now donate a small amount a month back that I'm in a better place. I had to send payslips with my applications to prove I was in that industry and it did take a little while.
I think there's one for care workers and other jobs - ask your HA if there's anyone that they can put you in touch with like that in your area. Or Google your job + charity.
What about colleagues at work? A few gave me stuff when I moved in here, some rugs for the floor, curtains and one sold me a halogen oven - they're cheaper than big ovens but they're better than a microwave, though a microwave is better than nothing.
Can you get some drawing pins? You can tack sheets up at the windows for now and when I had a little money I bought a cheap plastic washing line, tacked that above the window and hung a blanket over so I could fold it up on itself during the day. Not pretty but did the job.
Good luck OP, this stressful bit is worth it when you start to get things in shape and you know you're secure.