An aspiring doctor was killed in a horrific subway accident yesterday when she passed out on a sweltering Upper East Side platform and fell onto the tracks -- realizing what happened too late to escape an uptown train bearing down on her. Fatoumata Binta Amina Diallo, 21, "was cut in half," said one shocked witness. Diallo fainted at around 3 p.m. at the 77th Street/Lexington Avenue station, which was filled with schoolkids on their way home, said transit and police sources. The Bronx woman had been returning from a dental appointment, said her family. Diallo came to after falling onto the rail bed, and desperately tried to get out of the way of the No. 6 train by scrambling to the area between the north- and southbound tracks. But she couldn't move fast enough. She was pronounced dead at the scene. The young woman's death devastated her family. Close to 50 wailing mourners gathered last night at the West Tremont Avenue apartment she shared with her father, stepmother and brother. "The family's traumatized. The father can't even speak. This is just horrible," said a cousin who asked not to be identified. Diallo, a native of Ghana, had been studying at Borough of Manhattan Community College and dreamed of becoming a doctor, according to family members. She had just celebrated her birthday last Thursday. The accident horrified straphangers on the packed Bronx-bound train. "I heard the thump, the train hit something and it stopped," said passenger Nicole Katzender, 26, of Queens. Sandra Pereira, 47, also of Queens, described a chaotic scene in the tragedy's aftermath. "Everyone was waiting for the train, and they started screaming," she said. Riders said temperatures in the subway station were very high as the mercury outside reached 90 degrees, making it the hottest day of the year so far. With added humidity, it felt closer to 102 degrees, said AccuWeather meteorologist Mike Pigott. Straphanger Amber Shanks, 19, from The Bronx, said, "It's extremely hot down here. It's not safe." Source: nypost.com