Bernadette, 17, is yet to return home after she left on July 18, and her family is desperate for anyone who may have any information on her.
Mum Sarah Walker has asked the public to help her in distributing posters, hoping that if she gets them into every area of the city, Bernadette will be found and will return home.
Sarah said: "We have had no contact with her since 1am on July 20, when she texted me to say she would be home soon. None of her friends have heard from her and she's not accessed social media."
She added: "I can't eat or sleep properly. I miss and love my eldest princess so much, she's missing out on her baby sister, who has learned to smile and coo already. I have to think that she is hiding at one of her friend's homes, worried about coming home now that the police will want to speak to her, I can't think of any alternative scenarios, I just can't.
"I know my baby girl wouldn't be out in the open. She's scared of being out in the dark alone, that's what makes me think she's at a friend's house. I just wish someone would just say she's here and she's safe. I want to cuddle her, but right now I'd accept that she's safe and well."
Sarah's family originally believed Bernadette may have had additional clothing with her but have since found the missing items under her bed, so she would have been wearing all black with a denim jacket on.
She has a distinct lock of brunette hair on one side and blonde hair on the other, she wears black framed glasses and has a facial piercing.
Sarah has also been left concerned that Bernadette is viewed as medium risk in the investigation and is begging that she is moved to high risk.
She added: "I believe the police are doing their job, but as a parent I need more. I'm desperate for my daughter to be found. When will they up the risk to high instead of medium?"
A spokesperson for Cambridgeshire Constabulary said: "Hundreds of people go missing every year and we need to assess each case on its own merit and prioritise them in terms of threat for their own or others' safety, risk and harm.
"In this case, officers continue to carry out all available lines of enquiry in order to attempt to locate Bernadette who remains medium risk."