My parents never praised me for anything, they treated my sister like a princess

The unfortunate thing is that there are actually parents who do crap like this. They'll have a black sheep child and golden child. They'll pay all their attention on the golden child and just have the black sheep their to take any blame if the golden child does something wrong. But in this case the "claim" they tried to make their first daughter a perfect child so they could come back into her life and try to get something