Little girls in grown up bodies

I moved in with my mom. That meant moving in with my sister, too. I don't like my sister. She's selfish, spoiled and very immature. Just talking to her is a challenge. Even the most benign conversations turn into arguments. Why? Hellifiknow. She's very, very bossy and ignorant at the same time. I hate having her around my son. It's just hard.

When we were smaller, we were friends. Then we were on and off again as teenagers, depending on the hormone level. Then, for a minute there, we were friends again. But the person she has decided to be is just intolerable. I keep making excuses for her. She's not used to change. She's still getting used to us living here and is behaving in response to that. But she's almost 30 years old. It makes no sense that she's still behaving like an upset teenager. I honestly wonder if she has Aspberger's Syndrome - she's that resistant to change and becomes that angry when you tell her no. We have the same argument every other week. The food I cook on Sunday night is for my child. No, you can't have any. Yes, it is fair. You are a grown woman, you can make your own food. He's a toddler, he can't. No, it's not selfish for me to prepare food only for my son. He's a toddler. He needs to eat. I don't have time to cook during the week so I cook it all on Sunday night. No, you can't have any. I can't understand why she can't understand that. She can't understand why she can't get what she wants.

My son eats a banana every third day. In any given week, we may eat 3 bananas between the two of us. Little sis eats 3 in a sitting. She's incensed that she has to buy bunches of bananas every week. "It's time for someone else to buy bananas." Responds Mom, "I just bought $8 worth of bananas." They were $.49 a pound. That's a lot of bananas. She ate 6 a day. "Not you, the other someone else." Why? Because you feel the need to have someone take care of your needs? If your pocketbook can't support the outrageous amount of food you eat, that's not my problem.

She has a sense of entitlement that I cannot begin to understand. It would make perfect sense for a 15 year old. But once you're over 25, it's nonsense. On the outside, she's grown. But...internally...not so much.