The heartbroken teenager arrived at Belfast International Airport accompanied by her father Raymond McGuinness and her brother David yesterday afternoon, after catching a transit flight at London Heathrow.
Shannon, who was wearing a light black dress with white flowers, remained quiet but she could not hide her distress as she returned home. She appeared to wipe tears from her face as she waited for her suitcases.
Mr McGuinness explained that she had not only lost her mother in the ordeal but her best friend as well.
"It has been a very long and arduous day for all of us. It has been very difficult," he said.
"As for Shannon, it hasn't really hit her yet. Her mum was her best friend. They went everywhere together," he explained, before adding that he hoped his ex-partner's remains would be brought home "very soon".
Local media reports in Turkey are reporting that killer Cetin will claim he acted in self-defence. According to police sources, he confessed that he attacked Marion and her best friend Kathy because they had stolen his "dream".
His lawyer Alkan Tunal said that his client retaliated when the two Irishwomen attacked him and slashed his hand.
Prior to his alleged confession, Cetin claimed that Marion and Kathy had been kidnapped in port city Izmir and that his hand had been wounded while he tried to defend them.
However, this first explanation fell apart when he failed to clarify how he had returned to the women's rented townhouse in Kusadasi, 75 miles south of Izmir, where he had also been staying.
Cetin is expected to be formally charged for the murder later this week.
He claimed he was 17 years old, but concerns over his age have arisen. It has emerged that Cetin told tourists that he was 24 years old.
If he is tried as an adult, the bodybuilder could be sentenced to more than 70 years in prison for double murder, instead of a maximum of 24 years for a juvenile.
Cetin is thought to have stabbed and slit the throats of Newry natives Marion and Kathy in a wood near Izmir last Thursday, after they both opposed his dating Shannon.
Irish tourists, who met Cetin on their honeymoon in the tourist resort of Kusadasi in June 2010, claimed yesterday that he told them he was 24 years old.
"He told us he had no girlfriend because he was too busy, he worked a lot of hours and said he had no time," John O'Brien from Gorey, Co Wexford, said.
"He said he was 24 because he couldn't believe I was 28 and my wife [Joanne] was 25 with two children.
"We couldn't believe it when we saw the papers over the weekend.
"We looked at the pictures and just said, 'that's him'.
"It's absolutely horrific but you would never have known this guy could do such a thing.
"He seemed to get on with everyone."
Cetin, also known as Alex, is understood to have wanted to marry Shannon, who he had been seeing for two years, but her mother forbade it as Shannon was underage.
The women's bodies will not be repatriated until tomorrow at the earliest, it has emerged, because of the paperwork involved.
Ms Dinsmore's niece Ruby and nephew Robert are expected to stay in Turkey until tomorrow to deal with the procedures. It is expected that the remains will be flown from Antalya, 350 miles from Izmir, on the southern coast of Turkey, to Belfast directly.