Why do people think they can talk to me any kind of way?

I'm the youngest in my family (15) and I'm staying at my adult sisters house for the weekend. This morning she cursed me out b/c I didn't pick up her crying baby. ( I honestly thought she wasn't letting the baby cry on purpose, but I didn't know she was busy cleaning the house) I was laying in my bed on my iPhone. I started to cry and get really angry b/c I have no clue why I just don't defend myself. In the past she has send very mean things to me (dumbass) what should I do?

You're a human being not a doormat! Don't let your older sister or anybody else BOSS you around. Defend yourself.

Dude just relax man YOU NEVER KNOW HOW GOOD YOU HAVE IT TILL ITS GONE just show her that you care you know what they say kill her with kindness