I'm new here but I wanted to just throw in my two cents. I went to a non-russell group uni for undergrad (in archaeology, the course was far more practical and that's what I wanted), fell in love with it and then ended up (somehow) at Oxford for my Master's (the old MSt Archaeology that's now been discontinued); I am now doing my PhD in Iron Age Archaeology at the Uni of York.
My undergrad diss was a mess (still ended up with a first but ehh). We were given freedom over what we did, and we had a few lecturers in the dept that were leading academics in their fields so, I am sure Exeter has some of those. Though none of us were given access to primary sources and archives, and this was pre-covid!
I chose something theoretically linked to my Bachelor's for my Master's thesis as Ox but not in terms of era (this is fairly specific to historical studies tho). In terms of getting into Oxbridge, it is easier at Post-grad. I achieved a First overall but my offer was just for a 2:1 (60%). I went in with no idea that I was particularly gifted, moreso that Oxford was the best uni for me. That is, I think, where Ruby is going wrong. She's applying to Oxford cause it's Oxford, not cause it's the best university for what she wishes to study. At post-grad you gotta go where your specialism will be best known and understood. I found Oxford so hard. The expectations were immense, and the feedback I received was brutal. My marks and feedback only improved when I changed and developed my writing and my approach to academia. They don't suffer fools there, and they will tell you to your face if you aren't meeting their grade requirements. I was 2% off a merit, I got 63% overall, from when I was used to mid-to high 70s, much like Ruby. It was. A. Slap. In. The. Face. And it hurt. But it was what I needed. My research skills, writing, and editing have gone from what I realise was not sufficient to something much more suited to an academic career. I wonder how Ruby will deal with the harsh reality of Oxford, after being coddled by Exeter?
The subjects she's looking at are so, so broad. She's really going to struggle to fit is all into a word limit. I definitely did, and ended up writing 21k for my undergrad (I was able to shove loads into appendices).