The quality of candidates at UWS is worse. full stop. i'm sure you're willing to admit that. UWS uses the same marking standard as other unis, i.e. grades will be loosely distributed around the bell curve. Now, you tell me, is it easier to get a D against worse students, or around better ones with the same distribution of marks?
Your friend could be affected by numerous factors. For instance:
a) She may not have been able to transfer all her subjects over, and had to repeat some. Repeating a subject (or a similar one) results in a higher mark the second time round
b) if she lives closer to the city, her travel time has gone down, leading to more sleep, more absorption of material and more time to study
c) It is fun to say you're outside of the norm. Some people like to brag about hard subjects being easy for them. Your friend may be trying to do a similar action 'ohh im so not studying at all and gettin good (read: very average) marks'.
d) Uni is hard to get adjusted to for the first year. After this, it gets much easier, as you learn time management, effective studying techniques, etc.
And a person-by-person basis isn't particularly applicable here. Hiphop got credits and above at UWS, but at USYD, he gets a below credit average (from memory). He even is retaking subjects he's taken at UWS, yet is still finding higher marks difficult to attain. Is this a relevant way of comparing the ease of attaining marks at one uni over another for all candidates? No. It's only really relevant for the individual.