Berna Fidan is calling for a cold case investigation into the disappearance of Esra Uyrun who was last seen 11 years ago.
Berna is making the appeal to mark the anniversary of the last time her 38-year-old sister who lived with her husband, Ozgur, and two-year-old son Emin in Clondalkin in west Dublin was seen.
At 7.15am on the morning of February 23, 2011, Esra went to the shop but never returned home.
Her car - a silver Renault Twingo, registration number '08 D 23067' - was later found in a car park at the bottom of Bray Head in Co Wicklow.
There has been no activity on her bank accounts or her Facebook page since that day.
Berna says it is suspicious that her small purse was found in the boot of the car.
"Maybe she was put in the boot and it fell out of her pocket?
"A little tiny purse like that you would - if you are going to leave it in the car - you could slide it in the little compartment next to the driver's seat, or in the glove compartment."
While the case remains an unsolved missing person's case, Berna wants it upgraded to a cold case investigation, but not to a murder inquiry.
"How can I say I want it to go into a murder investigation when I don't know if she's been murdered, or if she's even dead?", she says.
According to Newstalk, Berna, who lives in England, will return to Ireland on Saturday to renew her appeals for information on the case.
"We need some form of closure, because this has just been torture for us for the past 11 years now.
"It's the not knowing of what's happened.
"It breaks my heart to look at my mom's face, and she's looking at me for hope - that I will come back with some news".
Anyone with information can contact Ronanstown Garda station on (01)-666-7700 or the Garda Confidential Line at 1800-666-111.
Esra is described as being 5'3" in height, of normal build with dark green/hazel eyes and sandy blonde highlighted hair.
She has a sallow complexion.
On the day she went missing she was wearing black leggings, a dark top, light brown boot and a green or denim jacket.