My comment on that lady teacher was rather glib. Further
reading of this story reveals that she originally
had some personal issues, which then led to alcohol abuse, and after that,
these offences. I think she carries a great deal of sadness, and her behaviours
have been those of a person who lost their way. But, none of that, as you ask,
answers that fundamental question of "why?". The sentence of 4 years + is quite a severe term, and maybe the courts want to send some type of message out.
The whole thing is puzzling to me.