I was at Oxbridge now 30 years ago and there were plenty of people there with undiagnosed autism. I suspect at least one of my tutors was!
There was also, at my college at least, a huge emphasis on welfare. I can remember in Freshers' Week coming out of the library talk asking "how did that end up being another welfare talk?" every talk we had from everyone in that first week seemed to be about who to get help from, where to go etc.
There were people who had mental health issues, and generally, as long as they came forward, there was plenty of help there. For example in my college I knew three who had taken a year out for mental health reasons, in one case restarting the year, in the other two they'd had a year of struggling and between them/tutor/welfare they decided a year out would help. In all three cases they completed their degree when they came back.
I know of further people who had episodes of struggling mentally, all of whom had support in various ways and none were sent down.
The only person I knew in my time there who was sent down did no work, and refused to engage when the tutors and welfare team tried to get to the bottom of why he wasn't working, but they gave him most of a term where they tried to help him, and tried time and again. It certainly wasn't a case of just writing him off immediately.
The scouts (college cleaners) were asked to be looking out for people not coping - a lot of them were very motherly, and people did cry on their shoulders at times. There was a system for them to report if they were concerned about someone, and the welfare would act quickly when told.
But at no time would I have expected parents to be called, except if it was emergency. I don't think they'd have been allowed to give details.
You could contact the college and see if one of her tutors is still there and they may be happy to come and talk to her. They may well remember her because being sent down is very unusual.
But I'm not sure that you will find it the closure that you are hoping for.
What do you want? Would it actually help her or would it bring up all the old feelings to the surface? What could they say, which would bring closure? Does she feel it would help?