The response to the disappearance and subsequent searches for teenager Gaia Pope is to be investigated by the police watchdog.
The 19-year-old's body was found in undergrowth on the cliff top near Swanage, Dorset, 11 days after she was reported missing on 7 November.
The Independent Office for Police Conduct (IOPC) said it would examine "actions and decisions" of Dorset Police officers.
Miss Pope's family welcomed the probe.
Her sister Clara Pope-Sutherland said the family "won't stop until we get answers".
"I did feel that it did take a long time to find her," she added.
"I'm very hopeful the investigation turns out some useful and truthful information.
"It's too late for Gaia but I'm not having anybody else go though what our family has gone through, it just can't happen."
Following Miss Pope's disappearance, searches by police, the coastguard and police helicopter - along with hundreds of volunteers - were carried out in the Swanage area.
Her body was found by police at 15:00 GMT on 18 November near a coastal path and field between Dancing Ledge and Anvil Point, close to where items of her clothing had been found two days earlier.
The IOPC said the case had been referred to the watchdog following an internal review by Dorset Police.
Director Catrin Evans said: "We are examining the actions and decisions of Dorset Police when dealing with the missing person report made in respect of a vulnerable young woman.
"We will also consider whether the force appropriately risk assessed, resourced and reviewed the missing person report."
Tests showed Gaia who had severe epilepsy and mental health issues had died from hypothermia.
An inquest into her death, which was adjourned until May, heard there were no suspicious circumstances or signs of third party involvement.
A Dorset Police spokesperson said: "We have an obligation to review incidents involving death or serious injury following police contact.
"Following a review it was felt the mandatory criteria was met and this matter was referred to the IOPC."