Hazel Polge, whose sister Rose disappeared in February, started an online donation page for mental health charity Mind and Dartmoor Search and Rescue in a bid to "prevent such tragedy" happening again.
More than £4,000 has already been raised for the charities.
Rose Polge, 25, was in her first year as a junior doctor at Torbay Hospital in Devon when she went missing.
Her car and some of her clothing were later found near Anstey's Cove, Torbay.
Dr Polge's body was eventually recovered on April 11. Her sister said Dr Polge had been working long hours and suffered "work-related anxiety".
Hazel added that money raised for Mind would help people who "like Rose may suffer acute crisis or distress", and help support those suffering from chronic mental health conditions.
Writing on fundraising website JustGiving, Hazel commented: "All Rose's colleagues are missing her hard work, friendliness and approachability.
"Her stunning smile, infectious enthusiasm, kindness and inquisitive nature made her popular with all people she met.