The older girl appeared in court Wednesday to face a juvenile charge of first-degree murder, the Chicago Tribune reported.
She was arrested Tuesday in Mundelein, 35 miles northwest of Chicago, shortly after she called police to say her sister, Dora Betancourt, had been attacked. She initially told police someone had broken into the house and repeatedly stabbed Dora, but when police told the older girl they found her hair in Dora's hands, the older girl allegedly confessed.
Police said the older girl told police the sisters argued the night before the stabbing because the older sister thought her efforts to run the house -- cooking dinner and doing chores -- were going unappreciated by Dora, the Chicago Sun-Times reported.
Still angry about the argument, the older girl allegedly woke up the next morning, grabbed a kitchen knife and stabbed her sister in bed 30 times, the Sun-Times reported.
After Wednesday's hearing, the older sister was put in secured detention. Prosecutors said they'll decide if she'll be charged as an adult in the coming weeks.