I'm guessing her grades have something to do with the tremendous amount of time she puts into every one of her assignments, compared to her peers. For example, if you look at any of her exam-related content (i.e., the 24h exams), you'll see she spends way more time on these than she should have. The same goes for any of her essays. But, of course, she's only able to do that because she does literally nothing else (sorry, but transcribing war poems for 30 minutes a day isn't exactly a time-consuming extracurricular). If Ruby actually committed to any extracurriculars (e.g., sports, a uni newspaper, research assistant, etc.) or had an actual job while at university, I'm sure her marks would suffer tremendously.
I study at an ivy league law school in the U.S. An essential aspect of a law school application here is the resume because it shows whether an individual has done something with their time at university or just studied day and night. The latter would not be a competitive applicant. In the grand scheme of things, Ruby's grades are actually quite mediocre, given that she does nothing all day but work to achieve these grades. I think a first is everything above 70%; her average was 74% (I think). If she worked 20 hours a week (for example) in addition to receiving a 74%, I'd be a lot more impressed.