Loved ones want justice for a Wellington PhD student allegedly murdered by her estranged husband on a visit home to Sri Lanka.

Apsara Wimalasiri had not wanted her "dangerous" ex to find out she had returned home, but he allegedly found and killed her just days after she arrived back in the country last week, a friend said.

Wimalasiri had made a last-minute decision to fly back to join in mass protests calling for the resignation of President Gotabaya Rajapaksa.

But her flatmate Joao Guilherme believes she never even had time to join the protests before her death.

He said she had been separated from her husband for about a year after discovering he had cheated on her, and she was seeking a divorce.

When she went home to Sri Lanka – a trip that was only supposed to last a couple of weeks – she did not intend to see him.

"She knew he could be dangerous. She wanted to make sure he didn't find out she was there. Very few people knew she was there," Guilherme said.

"She just wanted to move on with her life but apparently he couldn't.

"You believe you know the person, you love them, then find out they're just some monster.

"How can a guy just not accept that the woman is not interested anymore and believe they have the right to take the other person's life? That shouldn't exist."

Some months ago the Sri Lankan police were called after Wimalasiri's husband allegedly made threats against her family. Guilherme was critical of how police handled the matter and felt he should have been charged.

"[Her death] could have been avoided," he said.

Guilherme has been flatting with Wimalasiri for about two years, and said they became very close in that time.

"She was such a bubbly, happy person ... she would always be very positive about stuff, always helping people too."

Wimalasiri used to make friends everywhere she went, he said.

"It was a very beautiful thing to see."

Former schoolmate Kaushalya Madubhashini described her friend as "one of the brightest students" and "a famous character of our school".

She and other friends were shocked at what happened.

"She was the only one who knew the truth," she said.

"We, as her friends, want justice for her, that's it."

Madubhashini heard the news from a mutual friend.

"I thought it was a joke from someone ... but it really happened," she said.

Childhood friend Chinthana Deshapriya said Wimalasiri had a "strong and close bond" with her father, who died some time ago.

"His demise made her more strong and she shouldered the responsibility of her family with her mother," she said.

"She was always bubbly, talkative, funny, loud and everyone enjoyed her presence ... it's full of laughter when she is around," she said.

"She is loved by everyone as she was loving, humble, straightforward and she was always positive about things whatever life threw at her."

Victoria University of Wellington's acting pro vice-chancellor for humanities, social sciences and education Sarah Leggott said the university community was grieving the loss of an international PhD student studying in their applied linguistics programme who had returned home to Sri Lanka.

"The thoughts of the whole university community are with the student and her family. The university is providing support to impacted staff and students," she said in a statement.

"A commemorative event for the student is being planned by friends and colleagues in her school."

Other loved ones were sharing posts calling for justice for Wimalasiri, saying "no one is wrong enough to be murdered".

Another friend said Wimalasiri's "chill vibe and bubbly personality" would be missed.

"Right now, I am happy that I am abroad and won't see you in a coffin - so that my last memory of you will be the peals of laughter we shared when we last met in Kadawatha."