I could see her sticking with Oxford, especially as her identity has been focused on it. She is focused on the aesthetic and being honest, it is going to be a source of content for her. She is going to have university vlogs, and lots of back-to-school videos as she is doing now etc., but she might use her master's at Oxford to be a source of authority.
She has not been coy with Oxford, unlike her job etc. If she leaves Oxford, it would be rather humiliating for her, especially as she has branded herself on the perfect student image.
I think that will struggle with Oxford as a masters is very different from than undergraduate degree, especially with the workload and the quality of work that is to be produced. This is from my own experience and I was only getting low firsts at most at undergraduate, compared to Ruby who did get high firsts but she did get help from Blakeney and her other methods.
Besides her disadvantage with the subject, Ruby just seems so much more focused on her writing than her coursework. She really likes the aesthetics of Oxford and the study aesthetics, and the busy work.
I'm not sure how it would work, but I think that she would get a master's regardless of the grades unless it was a fail. However, if she dropped out, she would be making videos about how she enjoys learning for fun and that formal education is restricting akin to what she had done once her dissertation was submitted.