I agree, I would think about what is an appropriate expectation if a 19 year old, tailored a bit to your daughters needs, and leave her to it.
so most 19 year olds can make their own food, but will still have family meals. Your daughter finds eating together difficult, fine. But I would just leave her to make her own breakfast and lunch. She shouldn't need reminding of this and if she is going to go off to Uni at some point she needs to be reasonably independent.
It sounds like your daughter has decision paralysis and is worried about making the 'wrong' choice and being filled with regret. This is common in perfectionism. The way to move past it is exposure, so making the 'wrong' choice about e.g which birthday cake to choose, feeling a bit of disappointment and letting it go. In your first post you were trying to make things 'right' for her but that just makes it worse, as it reinforces that disappointment over a cake is a really big deal, and any negative emotions she has are for the family to fix. Encourage her to start making all her own choices as much as possible, and stop doing things for her that she can reasonably do herself, and she will learn a framework of how to choose, and how to deal with disappointment and mistakes.
I think part of the reason she is stuck is she is paralysed by fear of making the wrong choice (and finding reasons why she can't, like 'trauma') and hasn't understood that not making a choice is also a choice. Not choosing which school to do her A levels at or an alternative has left her doing nothing for 2.5 years, which is probably worse than any choice she could have made at the time.