No apologies necessary. Your sister is so selfish because she is immature. I know she’d hate to hear that but expecting the world to be organized around her needs and desires and wanting to be judged for her good intentions instead of her actions are “symptoms” of immaturity.
It’s not unusual for a kid to grow up with other people before family. It’s too easy to slip into old roles with familiar people who have to forgive you. But as you are finding out, this behavior gets old real quick once someone is in her 20s. People do mature at different rates. You and your youngest sister have, for reasons of your own, matured more quickly than middle sis.
Do keep telling her that, as an adult, she is accountable for her actions and that you all expect her to treat the family as nicely as she treats others. Otherwise, how will she learn? But I do suggest that you give your feedback in as loving a way possible so that she’ll listen. If you scold, nag, harshly criticize or put her down, she’ll get so defensive she won’t be able to hear you.
Go about your own business of growing up. You seem to be doing a fine job of it. Fortunately, your sister is getting older by the day and will probably grow up too.
I wish you well.
This article has been updated from the original version, which was originally published here on February 28, 2009.