Gable Tostee has been dumped by his Kiwi girlfriend who says he "hurt me in ways he said he wouldn't" and left her "emotionally starved".
Lizzi Evans was Tostee's shoulder to cry on during the Brisbane Supreme Court murder trial which saw him exonerated by a jury in October.
But in recent weeks Evans broke off her relationship with the 30-year-old Gold Coast playboy and returned to her native New Zealand.
"I said we had no future," she told Daily Mail Australia in an exclusive interview.
Evans said she was "frustrated" by his behaviour and emotionally hurt by Tostee, who she described as being "obsessed" with his "old life" which revolved around partying, drinking and girls.
"He wants to live like that forever," she said.
Evans was initially attracted to his quick wit and thinking, debating skills, occasionally chatty and outgoing nature and similar hobbies.
But said he was set in his ways, unmotivated, scared of change and unwilling to compromise: "It was either his way or no way," she said.
The pair were together for about a year, described as "an intense time with a lot of emotions obviously".
Daily Mail Australia first revealed Evans' role supporting Tostee throughout the ordeal of the nearly fortnight-long murder trial.
"We had hoped to begin a new chapter of life but he became resistant," she said.
"I just had no more to give in the end but he seems (unfazed) as to be expected I suppose."
She declined to go into the specific circumstances of their break-up - except to say it was not related to the trial - but rather his personal behaviour. She also described his supportive parents as "incredible" people.
Tostee's trial received international attention - with news anchors broadcasting live from the grounds outside the Brisbane courtroom - because of the involvement of the popular dating app.
His Tinder date, New Zealand woman Warriena Wright, plunged from Tostee's 14th floor Surfers Paradise apartment to her death on August 8, 2014.
Tostee - who regularly picked up women on Tinder and boasted of bedding more than 200 women in his lifetime - was found not to have culpability for Wright's death by a unanimous jury verdict.
Since the trial, Tostee has answered questions from TV news magazine programme 60 Minutes and members of a Facebook discussion group.
"I suffer brain damage every time I read a dumb comment," he told punters last week.
He also returned to the limelight after becoming the first person to drink a Gold Coast cafe's monster milkshake.
Tostee is studying architecture, friends said, and was hoping to leave the Gold Coast, perhaps to New Zealand with Evans.
But his hopes for a future with her seem to have dimmed.
Daily Mail Australia has contacted Gable Tostee for comment.
The 19-year-old disappeared without her wallet or mobile phone.