Malthus became a tetraplegic in 2016 aged 19 after falling from a horse in a workplace accident.
Rather than being placed in a rest home, she secured a place at the Trust's rehab centre for treatment as she adjusted to her new reality.
"It is such a vital centre for someone like me, who at 19 recovering from those injuries being put in a rest home would have affected not just my physical but mental health."
Epsom MP David Seymour, who attended the protest, said the abrupt closure was a blow to the young people who relied on the service.
"Being a young person and coming to terms with a disability is a difficult enough situation. Being able to do this in a custom built facility with people your own age makes it more bearable.
"The incredible stories I've heard from young New Zealanders about how much this facility has meant to them means we can't stand by and do nothing.
"I'm calling on the Government and the board of the Trust to get back to the table. This is about young people with disabilities. We should be doing absolutely everything we can to support them."