Seriously, after seeing the episode which mentioned Pinkie's full name I see her family as more like the Amish in image rather than sad. As they are referred to as the plain people, and her family is plain. While Pinkie is the life of the party. Pinkie learned friendship brings out the best in her, and if you watched the entire episode you would have noticed her family enjoyed the family she created at the rock farm.
As for her actions in "Party of One", she is a lot like me at times unsure if people like her or not. So will choose to be a wall flower and hide from others. I don't see it as evil, more like she is misunderstood.
This is my opinion, take it or leave it. As it is ether right or wrong it just is.... .