Your spoiled sister (Iris) would always want something and be a spoiled brat towards mom and dad. Iris thinks she is allowed to do or have whatever she wants, and may behave badly or disrespect others.

Iris: HEY MOM! Can I buy these cute boots their only for 500$ smirks and shows mom from the computer

Mom: sighs sweetheart can you say something about this...

Dad: IRIS NO!

Iris: BUT-

Dad: NO BUTS! GO TO YOUR BEDROOM NOW!

Iris: gets extremely mad like she's about to murder someone and goes upstairs into her bedroom and breaks some things