The only thing I find kind of weird is that your teacher "says to her all the time" how beautiful she is.
Anyway, I'm not a guy, but I am someone who used to have really bad acne and ended up taking medication after several years of taking good care of my skin and wearing minimal make-up (although I didn't not wear make-up for my skin's sake -- I just didn't see the point in make-up as a 13-year-old). Now, my skin's probably average and I do wear make-up, especially over the bad, noticeable spots.
Personally, I don't like excess amounts of make-up, but I think it's someone's choice for how they want to present themselves. Maybe some people really do find her beautiful, but maybe some people don't.
However, I would just like to point out that although some acne is caused by looking after your skin badly, not drinking enough water, eating badly, etc., some skin conditions are hereditary (as mine partly was -- although I am a sucker for a good Maccie D's) and have NOTHING to do with the amount of make-up. There is some make-up available which isn't as bad for your skin as others as well.