Daughter has blood pooling in her mouth.has anyone heard of this

Hi there I'm apealing far and wide in the hope of finding answers.....my 14yr old Daughter has experienced blood pooling in her mouth every two wks for the last 3mos.....shes had cameras up her nose and down her throat lots of blood tests and an mri scan with contrast and all tests come back perfect.....when this happens she has stomach pain...headaches and generally feels unwell but her stats are always good.....she spits large amounts of fresh blood every 20/30mins.....i hope someone has some answers on here we're getting desperate....

Has she gotten a blood test to check for anemia? My sisters gum would bleed and it was cuz she was anemic iron tablets fixed it. But if shes not she might have some blood disorder so i suggest takingher to a blood specialist

She's been tested for anaemia and blood disorders but all ok? There's no bleeding point in the mouth ie no marks no holes or scratches or cuts....gums are normal and healthy no loose teeth its a mystery but sum1 somewhere in the world must have come across it....and thank u erika90744 for your input x