It sounds like your DD is financially illiterate. You need to teach her. Give her a book to read like 'Dave Ramsey-Total Money Makeover' or tell her to watch 'the humble penny channel' on YouTube. Or watch Martin Lewis Money Saving expert website or videos.
Then put conditions on her staying, eg
- She contributes, split the utilities and groceries into equal shares minimum.
- She pays off her debt like it's an emergency
- Once this has occurred, she saves for a deposit like it's her next emergency
Don't take her word for it either, see the paperwork to ensure she is keeping her word.
If she won't show you or you don't trust her to stick to the plan, then charge her a nominal rent on top of utilities and groceries. Save this nominal rent for her, and when she wants to move out, give it back to her, for her deposit.
If she doesn't comply with the above terms, she is welcome to move out.
But be wary, even if your DS who is at Uni does have autism, and doesn't need the pressure of a job, be sure to enforce the same rules, if he comes back to live at home and works full time.
I don't think your DS should have gone to Uni full time, unless he was comfortable with the student debt, or you were in a comfortable financial position to support him. If not, he could have studied part time and worked part time, or explored other options like apprenticeships. Different treatment towards DD and DS will cause friction.