Champa, along with Harsh (3) and Himanshu (1), jumped into the water tank at a nearby under-construction site, Bhankhrota police station SHO Babu Lal said.
The three were pulled out by onlookers and rushed to a hospital where they were declared dead, he said, adding that the reason behind the suicide was not immediately known.
"Champas's husband had gone to work when the incident happened. Her parents have been informed and they are on way to Jaipur from Bikaner," the SHO said.