Lisa Squire said she had undergone "a month of utter heartbreak" as she begged eyewitnesses to come forward.
University of Hull student Libby was last seen on January 31 after a night out with friends when she was turned away from Welly nightclub in the city.
Lisa, from High Wycombe, Bucks., has previously marked both one and two weeks without her daughter on social media.
She said: "It's now been four weeks without our beautiful Libby. A month of utter heartbreak and despair.
"As a family we are incomplete. We miss her more than we could ever say. We just want her back with us.
"Please if anyone has any information no matter how insignificant it may seem, contact the police."
Detectives investigating the disappearance of the philosophy student have since admitted she "may have come to harm".
Libby's mum, Lisa, and her friends have previously helped officers with some of the items Libby chose to wear that night including a black denim skirt and faux leather jacket.
Most recently, police released new CCTV footage of potential witnesses who could hold "crucial information".
The video released by the force shows four individuals walking down a street around half a mile from where Libby was last spotted.
Investigators say the people pictured may 'have crucial information that could assist the investigation'.
The footage was taken from a camera on Oak Road between 1.13am and 2.34am on February 1.
The Sun is offering a £10,000 reward for information that helps locate Libby.
THE LAST SIGHTINGS OF LIBBY
11pm Thursday January 31: Libby is refused entry at Welly Club, Beverley Road, 4kms from her home. The student was put into a taxi home
11.30pm: Libby was seen staggering around outside her student digs on Wellesley Ave
11.45pm: CCTV captures Libby sitting on a bench on Beverley Road, close to the junction of Haworth Street. She was also helped by a motorist
12.09am: Police beliee Libby stayed in the area for about half an hour
12.30am: A neighbour hears 'blood-curdling' screams
January 3 midday: Forensic officers find screwdriver, claw hammer and lip gloss 40 yards from where Libby was last seen
Pawel Relowicz, 24, was arrested on suspicion of abduction in relation to Libby Squire and released pending further enquiries.
He was later charged with unrelated crimes of voyeurism, outraging public decency and burglary.
Humberside Police say Relowicz remains “under investigation”.
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