I’m really sorry to hear you’re going through this. Different, but I was at the end of my tether with the situation of a much-loved elderly relative living with us. The problems weren’t any fault of the person, but the stress and pressure were constant. I was so despairing, I felt there was no solution aside from nature taking its course, for which I felt profoundly guilty, and still do.
Nature did take its course and grief was tempered by relief, I’m afraid. Not just for my relative, who was leading a miserable existence, but for me too. And I feel awful about it years on, so I do understand the extremes of feeling caused by relentless pressure. Forgive yourself. Any dark thoughts are not what you really want. They are a product of stress. What you really want is your dd living a happy life, but at the moment you see no way to get there. You will all come through this, but it feels relentless at the time, and sounds like there are a lot of issues intertwined.
Is the University aware of what’s happening with your dd? Is it possible for her to ‘write off’ this year, and re-do it? That might take the pressure off her feeling that she’s falling behind, and maybe lessen her anxiety? One of my dc was going through some difficult things at university, dropped out, re-applied somewhere else and ended up having a happy time at the new one. Could she re-apply to somewhere nearer home, if she’s finding it too difficult to cope with being away?