The grief-stricken daughter of Marion Graham has said she cannot understand what drove Recep Cetin to allegedly murder her mother.
The teenager has told her family how she has been left shocked and bewildered by the killing of her mum and Kathy Dinsmore in Turkey.
Yesterday, 15-year-old Shannon was being comforted by her brothers and sisters, Karen, David, Martina and Lorraine, as final preparations were being made for her mother's homecoming.
Speaking to the Belfast Telegraph last night, her father Raymond McGuinness said his daughter is struggling to understand what turned the boy she loved into an alleged killer.
He said: "Shannon just keeps saying: 'Dad, why did he do it?' She can't believe it, she just wants to know why he's done this, what he expected to achieve.
"She's a 15-year-old child and for this to happen - it's very difficult."
Shannon arrived back in Northern Ireland on Monday evening - four days after the bodies of her mother and Ms Dinsmore were discovered in woods outside Izmir, a city on Turkey's western seaboard.
The young girl had been in a relationship with Cetin, a waiter also known as Alex, since last summer.
Cetin wanted to marry the teenager and became furious when her mother refused to give her blessing to his request. It is claimed he lured Ms Graham and Ms Dinsmore into a forest and stabbed them multiple times, before concocting a story that the two women had been kidnapped.
Mr McGuinness said his daughter is struggling to come to terms with what has happened.
"She has lost her mum - her best friend - and it's going to take a long time to accept that," he said.
"She was having a brilliant time this year. She had been to Adaland (a local waterpark) on Tuesday, on different boat trips, she had also been to one of the Greek islands."
Mr McGuinness said Shannon has recalled the hours before Cetin is alleged to have killed the two women, and claimed he had been acting normally.
"She said he left her to the boat trip that particular morning and was just the normal Alex," he said.
"He said to her that he was finishing at the end of the month - he was going to finish work early, and he was going back to his home place and he wanted Shannon to come with him.
"Shannon said to him 'sure me and mum will go up', and he said to her 'no, there's no room for your mum'.
"Shannon told Marion, but Marion was making plans to come home.
"I suspect that's when he decided that if Marion wasn't there that he could take Shannon back home to his place.
"It would never have worked. Shannon was coming home with her mum, she was starting school again in a few weeks' time.
"She had got her uniform and was ready to start back again. Shannon's life was here in Ireland, she went to Turkey for the sunshine and a holiday.
"No-one saw this coming."
Mr McGuinness also said he has asked Irish officials in Turkey to confirm his age.
"He said to me last year that he was 17, so how can he be 17 again?" he said.