A team of around 30 medics removed what amounted to Lakshmi Tatma's headless identical twin sister who was joined at the pelvis and who did not develop and separate properly in the womb - an extremely rare case.
"It went very well", said Mamta Patil, a doctor involved in the surgery at Sparsh Hospital in Bangalore in south India. "She'll be in intensive care for the next 48 hours."
The risky operation was expected to be in the operating theatre for 40 hours, but the surgery was over after 27.
Dr Sharan Patil, who led the surgery at the country's Narayana Health City, in Bangalore, said: "Fortunately, Lakshmi has one complete body with a near perfect set of organs."
The operation was expected to cost about £100,000 - but the hospital said it was covering the cost of the surgery.