she doesn't do her homework in the afternoon;这句中为什么用doesn't do sth,而不用doesn't to do sth

因为does 是助动词,后面需要跟动词原形.不定式也不行啊？~~不行。不定式不能跟在助动词后面。要是这么改下呢？把doesn't to do换成doesn't have to do可以不？doesn't have to do 可以的。意思是：她不需要在下午做家庭作业。