I love Pearl, she's sincere and protective. And the reason she was so mean to Greg at the beginning is because she was basically in love with Rose (as evidenced by the fact that she literally blushes every time Rose comes up) and Greg stole her away from Pearl. This is also why she is overbearing of Steven because of the fact that he is in a sense Rose. It's also why she pushed Connie so hard because Pearl saw herself in Connie and Pearl did those things for Rose and thought that the same should happen for Connie.