BUT... I think what the story is now is not that Kristina is the favorite per se... but that Kristina is always the needy one.
Molly, as she told Dex, learned early on that Kristina was needy... so she focused on not being needy and pushed herself to be "Excellent". But sometimes we all need TLC. I think that is the story. Molly does need to be shown care sometimes... even though she is the last to admit it. She is fed up with all the work that goes into being the "got it all under control" daughter who doesn't need her mom to fix her screw ups. Molly is fed up and exhausted.
