Pinky got her milk test back and she got an A+. The farmer let her out to knock some more things over if she likes. "It is very boring in the barn since it is raining day and night," the farmer explained to Hannah Belle, who always gets immediate detention for knocking things over. "So it will be nice for Pinky to knock things over."
The reason why Pinky doesn't get punished is because she is incapable of forming intentions, so she can't be held accountable for her actions. Whereas Hannah Belle is incapable of not forming intentions. Also Tangy is Pinky's mother, so everything that happens to Pinky happens with nobody in loco parentis. So there you have it.