I also agree with PP that some people with ASD can mature a little later.
I certainly found that my DB was mid 20s before he was able to hold down a course of study and living on his own.
At 18 he was like a young teenager and took several false starts at jobs and courses.
I don’t think you are going to manage a transformation if you say “these are the rules” but don’t be so glad she is back that you go back to as it was before.
I think she needs a routine, but start with avoiding stresses/arguments /pressure to get a job. So she has to get up in morning and internet is disconnected at night.
If I was 18, slept all day, knew my parents were fed up with me, failed at keeping a job, gamed all night, wasn’t sure whether I will “succeed” at anything, lived like a slob, I’d feel awful but I don’t think I’d admit it.
Of course it depends on her/your family but I would try to regularly have small positives for her, as in when you are in the moment and something is good, tell her immediately. Not her appearance. But any efforts or compliance on her part. Anything at all that is genuine and keep it up even if she ignores you.
Like a 14 year old I’d be making food/expecting eating at regular times. Gently splitting up chores “which do you prefer to do” etc
I wouldn’t apply for anything for her. I’d bring things to her but leave it for her to instigate. I’d try to be very much on her side about rejections. “Well done for trying” “what’s next?” “You are able to do it, they probably wanted x, y and z. You are able to get x, y and z” “what do you think about this etc”