This is all very good advice, particularly this.
With an autistic child you particularly run the risk of this becoming something she continues. If she expects a partner to pay for her she may find some fool (even if not this one) who will tolerate and sustain her for years, she may eventually realise that having done this, she has left behind a career and her own potential. The cost to get long term will be very damaging. For her self esteem, for her own success outside or a relationship. Does she work now? How does she get money? Is she struggling with employment because of the neuro diversity? These might be explainers in why she is behaving how she is
I have to say that from lurking on autism threads, not necessarily on here, some on reddit, I do see quite a high proportion of adults with autism, many of them female, saying they can't work because of their autism but with no particular explanation as to why they can't work. Just things like they completely fall apart if you put them in employment, but they're able to cope with other things. They've more often than not found a partner or husband who is the only one working and they've quit work since being with this person.
There was actually a thread on here afew weeks ago in precisely the situation, a woman said she'd never been able to work most of her life because of autism and then she realised that in her advancing years she didn't have a pension of her own and that her entitlement to a state pension would be very low, because she's paid almost no NI. It's the realisation that relying on somebody else is far from an easy solution.
These are level ones and the self diagnosed. I'm not talking about those with moderate or more severe needs. Possibly with a bit of support or finding the right role for them they could work.
I agree that op should encourage her daughter to be self reliant earn her own money and be able to make her own choices in life.