I'm low income self employed. I have a student ds, and in autumn I'm going to become a student too.
We're used to living on shoe strings, but it's going to be 'interesting times', as I'm visibly disabled and struggle to get enough work every week as it is, and he's already failed an important exam through having to do more paid work than revision at exactly the wrong moment.
It's the reality of trying to over reach ourselves and there's no resentment. We all in it together here and I can't imagine not sharing out the baked beans between us frankly.
Of course you're NBU to expect DD to pay for food, but depending where you live if she now can’t find work, then something has to give, as you're also responsible for letting this situation unfold the way it has.
It sounds like the immediate problem is dd hasn't grown up knowing the family’s finances, or been expected to take more responsibility for herself earlier, aware of how precarious the balance is, and how to pre plan, squeeze something from nothing etc.
That skill gap has to be partly down to her parent/s even if it was well meant as protection. You can't go protecting them from the truth, but still expect them to recognise it anyway. That's not fair.
I think you should stop worrying about upsetting her, and sit down and explain it all to her, apologise if it's come as a bit of a shock, as you no more meant to cause her a sudden problem than she did you, and go from there.
If you're self employed, you must be used to trying to find opportunities, new customers, cost cutting, and scrabbling around a bit, surely? If you haven't already given her these skills, you should be sharing them with her now.