Baffled doctors have no idea what is causing the bleeding, which is steadily getting worse, and have dubbed her the "Mystery Girl" as they struggle to come up with a diagnosis.
Until they do, the teenager is forced to stay at home as the bleeding could start at any time, and must cope with the stigma of her condition which means she has lost most of her friends.
Her mother, who is terrified for her daughter says she has to shake her every morning to check she is alive said:
"Every morning I have to shake her to see if she is still alive. It's absolutely devastating. It happens every single day. We've just gone through 12 days of solid bleeding from her tongue and scalp. She is sick four or five times a day, vomiting blood."Last July, the teenager woke up with blood seeping out of her eye. She was rushed to hospital by her terrified family, but doctors could do nothing.Soon after, blood started seeping from her ears and from under her fingernails.
In the last couple of months the mysterious bleeding has spread to her scalp and under her tongue.
Cath said that her daughter had been coughing up blood and suffering from excruciating migraines for a couple of years before the bleeding started, meaning she was often to ill to go to school.
"It feels like we are living in a horror movie.At first it was only her eye. She woke up in a pool of blood. She came downstairs with the blood pouring from her eye. We rushed her to A&E but they could do nothing for her.
"Then it started coming from inside her ears, big blood clots, and then from under her fingernails. Recently, she tipped her head upside down and blood started spurting out from her scalp.
"The strangest thing is that her eye can be pouring blood until her face is covered and then suddenly it stops and the whites of her eyes are clear.
"The bleeding comes from the base of her tongue, a string of blood. She has to sit there with a cotton pad in her mouth to stop her swallowing blood."Cath, who works as a shop assistant in her home town of Stoke-on-Trent, said her other daughter Leigh, 25, and her dad have to stay with Marnie during the day as she cannot be left alone.
"I wake up in the night with her vomiting blood and then I have to go to work. I can't think of anything else, it's a constant worry." one of the worst things for the family is the reaction of other people when they see her daughter.
"There's the scare factor. We go to A&E all the time in a panic at the symptoms but there is nothing they can do. Last time we were there everyone was taking pictures of her and saying how disgusting it was. I had to take her outside, where she passed out."
Marnie said the worst thing about her condition was being unable to leave the house or carry on with her life. She said:
"I's weird, scary, really scary. I woke up the first time in a pool of blood. I walked downstairs and my eye was bleeding and the whole side of my face was covered in blood. My family were so shocked.
"I applied for a hairdressing course but I had to stop for fear of bleeding on the customers. I've lost most of my friends, they don't want to see me. I'm always at home. My life is on hold, I can't go to college.
"My eyes are the most shocking thing. I wish the doctors would just find what it is. No one has ever seen anything like it before."
Her mother Cath said she wants to raise awareness about Marnie's condition. She said:
"We know there will be silly comments, people calling her a vampire. But we hope someone, somewhere will have witnessed it and give us something, anything to help.We want to raise awareness, there must be someone else in the world with this"Marnie has been confirmed she does not have a brain tumour, no blood diseases, no clotting disorders - but doctors are unable to put their finger on the cause of her bleeding.
An ultrasound showed her liver, kidneys, womb, ovaries and organs are all functioning perfectly - as well as her ears, eyes, nose and throat. MRI scans, CT scans and multiple blood tests also all showed up normal.
The teen is currently waiting to see a gynaecologist to determine whether the illness, which gets worse around her period, is linked to her uterus
Source - MirrorUK