Chennai, Feb. 12: An eight-year-old playing Big Sister to her brother who “watched too much TV and did not study” got burnt to death after playfully threatening to kill herself if he did not mend his ways.

Playing the disciplinarian in her mother’s absence, Rathi Meenakshi, a Class III student of Arignar Anna Matriculation School in Madurai, apparently doused herself with kerosene to warn her four-year-old brother to get back to his books.

But a matchstick she must have lit as part of her role-play blazed horribly out of script, the flames first catching Rathi’s dress and then engulfing her body. She died in Rajaji hospital of severe burns last evening.

Sources said Rathi declared before death that she had only intended to “threaten” her brother, who is in pre-primary school. But hospital authorities refused to confirm this.

Police said something seemed amiss since it was unlikely that Rathi, a class topper, would resort to such extreme measures to force a four-year-old to “study”.

The boy is believed to have panicked at the sight of his sister burning and rushed to the floor below to get help. He was unable to say anything more, the police said over the phone from Madurai.

It is not known how many people were in the house or what kind of family - nuclear or joint - Rathi comes from. Her mother, out shopping when the incident happened, is in shock. Her father Murugesan works in Singapore.

Preliminary investigations revealed that the parents frequently quarrelled whenever Murugesan was in town. Rathi’s mother apparently threatened her husband off and on that she “would end my life by self-immolation”.

The police said it was too early to say if the girl’s dress accidentally caught fire or if she carried her threat too far. But it was possible she may have “internalised” what she heard her mother repeatedly say and taken a shot at self-immolation when nobody was home.

Rathi was buried last evening. The police are investigating the matter.