And what precisely had she done that required extreme punishment before that? She's not my most favourite student in the world, but I do consider the addiction an illness, not a crime, especially considering the way it came about. The love potion, for which she was punished by suspensions and being sent to magical boot camp, iirc. Under-age drinking, for which she's not the only one responsible and which was largely aided and abetted by her guardian. The fight with Jubilee, for which they were both punished.

If I'm missing something else, do feel free to point it out and we'll add it to the list. But do bear in mind that no-one's completely crime-free here, if you want to start demanding consequences.