One of the twin girls is found in the other stomach

A 9 - year - old girl in Athens appealed that her stomach hurts so she asked the doctor and found that there was another twin girl in her stomach.

I do not understand what it is saying, but the details are from the following.
Girl's twin found inside her stomach - CNN.com

According to Larissa General Hospital in Athens, Greece, I examined a 9 year old girl suffering from stomach pain and found that a fetus about 6 cm in length was in her stomach. This fetus is so-calledtwinsOriginally it was supposed to be born, but the other side (= now a 9 - year - old girl) seems to have been absorbed in the womb. This is a phenomenon that occurs with a probability of 1 / 500,000.

The fetus found in this stomach stomach remained in the state of so-called "embryo", and it was said that the shape had the fetus itself, the head, hair, eyes, etc. There was no umbilium or brain.