Mother-in-law plans expensive ski vacation for the entire family without asking whether the rest of the family can afford it: 'I find the way she went about it kind of manipulative.'

They've gone on way too long without telling her that enough is enough.

Have you ever been in a situation where you feel like you can't say no to a fragile person because you don't want to hurt their feelings? Maybe you have a friend who always puts herself down, saying no one wants to hang out with her. You might feel pressured to say yes to her every time she asks to hang out because it might make her double down on this theory that nobody likes her. That's admittedly kind of a bad spot for her to put you in, but if she has low enough self-esteem and you're avoidant enough to always say yes to her even if you don't want to, you might continue with such an arrangement for a long time. 

Most people do not venture out of their way to hurt people's feelings. In fact, a lot of us make far too many social decisions out of fear of hurting someone's feelings, and it hurts us in the end. You should be able to tell your friends you can't afford to go to the restaurant they want to go to without hurting their feelings. There's literally nothing wrong with telling someone in your life that you're uncomfortable with how much access they have to you, and that you need some space away from them. There's even nothing wrong with being open and honest about being mad at someone, especially someone you love. But a lot of people swallow their emotions for the sake of keeping the peace, and that's where resentment starts and grows.