女儿班上的一个老墨家长就是这样. 听说老师生病,马上送鲜花, 第二周又给一堆自己家种的苹果.
no matter the teacher is good or bad, that is her own bussiness not for our to judge, but as parents we shall do best try to help and be good to teacher. I think if your sister gives her 150% effort it wil changes lot better.
Also I think it is complicated in your niece's situation. You can't simply say who is right and who is wrong. And lots of time it doesn't matters. All you want to do is to restore the healthy relationship. SO don't blame the teacher nor your niece.