The actress, 38, headed downstairs in her Venice Beach apartment on Thursday where she discovered her family member unconscious, TMZ reports.
The star is said to have immediately called paramedics, but the team tragically could not resuscitate Vaneza after transporting her to hospital.
The site reports that autopsy results indicate Vaneza died from natural causes, and sources claimed she did not have any history of substance abuse.
Vaneza’s mother Lisa Centeno paid tribute to her daughter on Facebook. She wrote: ‘Vaneza, my sweet, sweet beautiful baby – your passing has left me destroyed forever but I know you are at peace in Paradise. I love you, my alpha child.’
Friend Francisco Gomez added: ‘It’s still not registering that you’re gone. The world has lost a truly beautiful person.
‘Spread your wings wide & touch the stars. You will forever be missed.’
DailyMail.com has contacted Rosario’s representatives for comment.