A Hampshire teenager, who fell to her death from a motorway bridge, had reported to police she was the victim of a sexual assault days earlier.
Sara Clark was interviewed by police after reporting a sexual assault
The family of Sara Clark, 18, believe a delay in a police follow-up call over the allegation led her to jump from a bridge over the M27 on Saturday.
After reporting an attack, Miss Clark was interviewed by police who said "her allegations were taken seriously".
The matter is now with the Independent Police Complaints Commission (IPPC).
Miss Clark's mother Amanda Clark, 44, said she spent several hours with her daughter on Wednesday after police called to say she had reported a sexual assault.
"They [the police] said they were going to call her on Thursday and Friday," said Mrs Clark.
"She was so depressed as she thought no-one cared or they did not believe her.
"Come Friday evening and still no-one [had called], she was really, really upset about it. She could not cope.
"If they [the police] were there for her, if a phone call to say they were investigating she would still be here today."
Amanda Clark said her daughter was worried 'no-one believed her'
Sara's body was discovered by a lorry driver in the early hours of Saturday on the westbound carriageway of the M27 near Southampton.
Miss Clark's sister Sabrina, 24, said: "She was looking for support to make sure people believed her - she did not feel she was believed.
"She said she was waiting for a visit from police."
Miss Clark was interviewed at Totton police station when she reported the attack.
She was then taken to a sexual assault referral centre for medical tests and more interviews.
She had further blood tests at hospital in Southampton before two detectives interviewed her alone at home on Wednesday afternoon.
Miss Clark's body was found near junction two of the M27 on Saturday
A statement from Hampshire Constabulary read: "We can confirm that she made an allegation of sexual assault to us in the early hours of Wednesday May 30 and patrol officers were deployed to the scene immediately.
"They arrived within a few minutes of her call, and the location was cordoned off and subjected to forensic examination and search.
"Specialist investigators were called out and a full investigation commenced, including taking her to Hampshire's Sexual Assault Referral Centre where she was spoken with, and supported by a sexual offences interview trained officer."
Police said inquiries had continued since then into the incident.
A post-mortem examination by a Home Office pathologist revealed Sara died from head injuries.
The Totton Road Deaths Investigation Unit is appealing to drivers who travelled on the westbound section of the M27 between 0330 and 0430 BST on Saturday to contact them.