Vanda Moran, 41, whose sister Rachel was murdered in January 2003, died in hospital from complications following exposure to chickenpox.
She had complex health problems related to long-term diabetes, which led to her having both legs amputated and left her partially blind.
Her parents, Ray and Wanda, believe she never recovered from the trauma of losing her sister, and hold Rachel's killer, Michael Little, partly responsible.
They believe Vanda neglected her treatment from the moment Rachel went missing until Little was convicted of her murder more than 10 months later.
Mr Moran, of Hall Road, Hull, said: "That period of neglect lost her something that, in her condition, could never be recovered and as a consequence I am convinced that Little and his actions certainly contributed to her premature death.
"He took away part of Vanda on that New Year's morning and started a steady decline in her general health, leading to her many operations and hospital stays. That full year, I put down to Michael Little. Without a shadow of a doubt, he's killed her."
They also paid tribute to Vanda's dignity, courage and strength of character, which allowed her to live an independent life right up to her death.
Mrs Moran said: "She went through a hell of a lot but she didn't want to be a burden and she never was. She never once asked 'why me?'"
Mr Moran added: "She fought every adversity with courage and bravery. She kept her pride and her dignity and she would not give in to her illness. She was kind, caring and proud."
Rachel, 21, was abducted by Little, a complete stranger, while walking home early on New Year's Day, 2003; her body was found a month later in a cupboard outside Little's flat. She had been stabbed to death.
Vanda will be buried next to Rachel tomorrow in Hull's Northern Cemetery following a service at noon at St Vincent's Church in Queens Road.