The Queen wears gowns and tiaras almost always and refers to this as her working uniform. Eileen prefers smart casual trousers and tops especially when flying. This has caused some disapproval but the Kingdom generally can see Eileen does have a point here. Tutus are no good to anybody when caught in a cross wind!
Eileen can and did dress up during her time in the Palace, which, for ceremonial occasions, she doesn’t mind, being glad to play her part. Where Eileen resents is when the Queen expects her cousin to “doll up” for private dinners and things like that. Eileen has no problem with the Queen laying down the law, it is the monarch’s job, but to tell her own cousin how to dress is a step too far. Eileen never looks scruffy. She has far too much pride for that and, for Eileen, that should be enough to satisfy the Queen. Naturally, given the growing antipathy between the pair, it isn't.
Jenny prefers to wear smart casual skirts and tops. The Queen approves (given the girl is a hybrid, the monarch does not feel Jenny should wear quite the same clothes as she herself does. Jenny, if she knew about this, would tell the monarch to stuff her tiaras and gowns and wouldn't wear them if someone paid her to do so).