A Florida woman, 21, has been charged with first-degree murder for fatally stabbing her sister after learning she had been making out with her boyfriend.

According to reports,  Fatiha Marzan killed her younger sister, 20-year-old Sayma Marzan, at 4:30 a.m. on Sept. 26 in the bedroom they shared in their family home in Orlando.

Fatiha had just found out that her long-distance boyfriend of five years and her sister had been flirting with one another in messages exchanged through a video game they played together, the Orlando Sentinel reported.

After finding out that her lover had told Sayma he loved her, she allegedly made the decision to murder Sayma.

Two weeks prior to the attack, Fatiha bought a “dagger style knife set,” according to the investigators.

She hid the knives in a closet and waited until her family members went to bed before pulling out a knife and stabbing her sister in the chest three to four times in the bedroom they shared, police said.

Fatiha called 911 hours later at 7:30 p.m. and reportedly said she stabbed her sister.

At 7:30 p.m., hours later, Fatiha apparently called 911 told them that she had stabbed her sister.

Deputies responded and found Sayma dead body inside the house .

According to officials, Fatiha admitted to stabbing Sayma three to four times, specifically in the heart.

She is being held in Orange County Jail without bond.