Talk to Pediatrician on Vomiting At Night

Aoa doctor...my niece is 3 years old.and weighs 11 kg. from the past 6 months she is sick.she had a severe blockage in chest.she was treated with hyzonate inj. nd nebulized. she was admitted in 2 hospitals nd they were also looking for a foriegn body so they did a ct scan which showed no evidence of any foriegn body. nd she was discharged but she is consistently vomiting from day 1 of her sickness at night only.. during daytime she is fine but at night she vomits 2 to 3 times sometimes 4 to 5 times. we have done ultrasound which was normal nd some tests advised by the doctors which include h pylori..alll of these were negative..everything seems to be fine but she doesnt stop vomiting nd sometimes she vomits blood also. i am very much confused nd her parents are depressed now..please can anyone help me regarding her condition..i will be much much obliged