I think that your friend's letter is immature, disrespectful and arrogant.
Regardless of any moral issue regarding elitism/discrimination that she is trying to highlight, to send a pompous rejection letter to Oxford is pathetic and defeats any issue that she was trying to raise; if your friend decided that Oxford was not the university for her, that is her choice, but she should have rejected in the normal mature way. Yes the university would send a similar type of rejection letter, but they are perfectly qualified to do so, as in this case, it is us, the students, applying to and trying to impress a prestigious institution against huge competition, not the other way around.
I may think this way, perhaps, because I am some 7 years older than most of you, as it seems to be a typical immature rebellion that a teenager would be proud of, that many of you are finding "epic" or "legend", which she may come to regret. (I would not like to label all teenagers this way, as there are many that are very mature)
Regarding elitism, I would love to attend Oxford University, I do not come from a public school, nor do I even come from a middle class background, I come from a single-parent, council-housed, working-class background. I do not find a grand, formal setting, like Oxford, intimidating, in fact, I find it inspiring. Oxford can't do much about their beautiful grand old buildings that intimidated your friend, but if she feels tortured by 3 lecturers interviewing her from behind a large desk with her seated on a stool, I suggest that she hide at home and never enter the real working world, as having been in the working world now for the past 7 years I can advise her that she will probably have some more horrific interview experiences to come. As someone else stated, future employers may not look kindly upon this when researching a candidate, I know that I certainly wouldn't, as an employer I would be worried about the lack of respect and immaturity that the letter shows, I would be worried that she would not be able to feel comfortable in certain situations and may not develop good relationships with colleagues/clients from different backgrounds.
It seems that your friend had made up her mind about Oxford before she arrived or she had some kind of inverse snobbery to her nature, I could be mistaken, but the fact that she sent this immature letter seems to hint otherwise.
Coming from the background that I have and having had a varied work career, I have met a huge variety of people and I have a wide variety of friends, those from public schools to those from working-class backgrounds. All my friends are lovely from either background (obviously or they would not be my friends), however, I can actually say that I have met far more inverse-snobs, those who like to preach hate on those who are posh, than those who are elitist snobs, probably as it seems to be far more acceptable these days to "toff" bash and those that I know from more privileged backgrounds are so worried about being labelled a snob, that they go too far in the other direction, giving excuses for unacceptable behaviour of others as an example, in fear that they would be labelled a snob for disagreeing with the behaviour.
I think it is very dangerous to set quotas, standards to be achieved of percentage of working class students/ethnic minorities etc. I would be horrified to learn that I got offered a place at Oxford, due to my state school and working class background and that another candidate, who had better grades/performed better in interview, was rejected in favour of me, as he was from a public school. I would hope that I got into the university based on my academic merit and interview performance. If there is a huge majority of public school students at Oxford, it is not the problem of the university, it is either that the some state schools are failing, or that there is a culture of indifference towards learning in certain areas of society or that some academically able working class students are not applying either due to their own inverse snobbery or that of others, who have told stories of Oxford being intimidating/elitist.
Just a note on fees, I received a prospectus from one of the colleges at Oxford recently, which states that the fees are income assessed, so those from lower income families could be paying £3500 per year in tuition fees and there are generous bursary schemes of up to £14,000 during the course of the degree on top of the government bursaries.