Isla Bell's body was located at a Dandenong tip in Melbourne's southeast in November 2024, six weeks after she was reported missing by her family.
Police originally charged Marat Ganiev, 55, with her murder, claiming he killed the teen in the early hours of October 7, 2024, before hiding her body in a fridge.
The charge was downgraded to manslaughter as the case entered the Victorian Supreme Court, but prosecutors withdrew that offence on Tuesday, citing insufficient evidence.
Ganiev has instead been charged with attempting to pervert the course of justice, with a new trial date yet to be set.
Ms Bell's mother Justine Spokes on Thursday took to social media, calling on the community to hold a peaceful rally in honour of her daughter.
"Isla never got her vigil," she said in a video posted to Instagram.
"I really want to welcome people into this space with no judgments in their mind.
"It's not about thoughts. It's just about arriving in that space with an open heart."
The vigil will take place out the front of Melbourne's State Library at 11am on Saturday.
Rally-goers are being encouraged to wear orange, a colour associated with activism to prevent and eliminate violence against women and girls.
Ms Spokes urged people to remain peaceful on Saturday, saying she had spent the past few years being angry and rallying.
"I'm tired - I'm so tired," she said in the video.
"And that anger, I know it catalyses change, but underneath all that anger is just so much sadness and grief."
A second man charged in relation to Ms Bell's death had his case discontinued on Tuesday.
Eyal Yaffe, 59, was originally accused of assisting an offender and attempting to pervert the course of justice, but prosecutors withdrew the two charges and he walked free from court.
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