Dr Rose Polge, 25, who worked at Torbay Hospital in Devon, was found off Portland Bill, Dorset, in April.
Hazel Polge, who said her sister worked long hours, has set up a fundraising campaign to help "prevent such a tragedy" happening again.
Torbay and South Devon NHS Foundation Trust refused to comment about Dr Polge's health or work situation.
More than Â£4,000 in donations has been raised for mental health charity Mind and Dartmoor Search and Rescue, which helped look for the missing junior doctor.
Dr Polge's car and hoodie were found near Anstey's Cove, Torbay in February.
Writing on a fundraising website, Miss Polge said: "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."
She said she was a "sweet, beautiful, kind, loving woman" and "she will never be forgotten".
Regarding the fundraising, she added: "Even if just one person was saved, to their family that would be everything."
Dr Rob Dyer, medical director at the hospital trust, said: "Our thoughts continue to be with Rose's family and loved ones as they struggle to come to terms with her loss.
"I believe they are entitled to privacy and I do not wish to comment publicly about Rose's health or work circumstances.
"I know from experience just how challenging the demands of the role [training as a junior doctor] can be [and] at Torbay Hospital, we take our duty of care to staff very seriously."
The BBC understands a note found in Dr Polge's car related mainly to personal issues, but included a passing reference to Health Secretary Jeremy Hunt.
Friday 12 February - Rose Polge's car is found in a car park near Ansteys Cove in Torbay
Saturday 13 February - The family and boyfriend of Dr Polge join more than 100 people searching the area around Ansteys Cove
Sunday 14 February - Torbay Hospital confirms that Rose Polge works there as a junior doctor.
Monday 15 February - Colin Smith of Royston Hockey Club, where Dr Polge played, said: "We just don't know what we can do."
Tuesday 16 February - Dr Polge's family release a statement saying they are "overwhelmed" by the support from her friends and colleagues
Friday 19 February - Police announce hunt for Dr Polge has been scaled down, saying there is "no structured search going on"
Friday 1 April - A woman's body is recovered from the sea east of Portland Headland in Dorset
Monday 11 April - Police announce the discovery and say relatives of Dr Polge have been informed
Monday 18 April - Police confirm the body is that of Dr Polge
A junior doctor whose body was found in the sea suffered from "work-related anxiety", her sister has said.