I went for an open day to my uni back in 2003 (am I really that old?). It was about an hour away on the train, so I could easily get there and back in a day.
My dad came with me. I would not have coped otherwise.
I am not ASD, or anything else. I went to uni and lived there for three years. I never moved back home - I moved back to my home city, because there is nowhere better, but I have never lived with my parents since I left in 2003 (except for holidays etc).
And yet the thought of doing that alone would have scared me shitless. Which is madness, but there it is. I'm really glad my dad came with me, I felt safe and found it easier to engage on the day.
My kids are only little, but I will be guided by them if and when the time comes - if they don't want me there, and it's ok, then I will let them go alone. If they want to travel to the other end of the country and stay for a couple of nights, I might insist on travelling with them but letting them do the uni bits alone while I go shopping or something. But that's years away yet.
Is that at all possible, OP? Go with her if she needs to stay overnight, but not actually attend the open day with her? Let her do that and meet up later and perhaps have a nice meal and hear all about it?