Younger sister (paraphrased): "mom and dad aren't respecting *an agreement they have* and say that because they're paying for X, they can decide to change the agreement whenever they want, and I feel completely disrespected, and it's not fair, etc, etc, etc!"
Me: "Yep. It ISN'T fair, and you did have the agreement, and they aren't respecting it. And it's typical, and it's how they deal with boundaries when finances are involved. It's frustrating. I understand. So you have 2 choices: you can figure out how to be independant, set your boundaries where you want them, and enforce it. Or you can calculate the amount you need to get there and determine that you can take the emotional bullshit for X amount of time in order to achieve freedom. This is your opportunity to decide how you value the $ vs bullshit tradeoff."
To be clear: I understand the frustration. I get it. But learning how to put dollar amounts on what you are and aren't willing to put up with, and organize your life so you won't have to put up with it if you decide it's not worth it? That's a life skill more people could stand to learn that young.
And frankly: my parents habit of completely and utterly disregarding any boundaries or necessary respect for people who are financially dependant on them is why I, at 22, made the choice to live on 20$/week of groceries, and put THAT on a credit card and pay credit card interest rates for 6 months until I could afford it, rather than ask my parents (who were bringing in a half-million a year) for a few hundred dollars to get me through. Sometimes, 20% interest is cheaper than the bullshit you'll have to swallow if you don't pay it. I love my parents, but man, never again will I be in that position.
And yes, that attitude deals with a LOT of baggage and has changed my relationship with money. Sorry, sister. Best you learn the lesson early.