I am always interested in Stats and I had a good look at Durham's stats from last year. There are certain niche subjects that tend to attract more Oxbridge calibre private school DC and it looks like they make earlier offers in these subjects using their historic data (not sure what your DD's friends subject was but I guess it could be a subject where they entice such candidates with lower offers).
In terms of wanting students - Most of the top Uni's/competitive courses will want the students they are making offers too....contextual or not, given that the DC will all have the course predicted grades in order to apply.