But four days later Wowo died surrounded by family. Mahanga, then aged 33, was sentenced to three years in jail for the manslaughter.
Kate McGrath said her one and only experience with domestic violence was the death of her sister-in-law, Wowo. It had been a harrowing experience but out of the tragic death they wanted something positive.
"We are here to tell you it's never okay for anyone to abuse you physically or mentally. This happened to Wowo, who was strong and outspoken, but she couldn't reach out to her family. We hope you will make a different choice," Mrs McGrath said.
"The biggest lesson from this is to speak out as soon as possible. The longer the abuser gets to push the boundaries the higher and higher the violence will become."
John McGrath said he would never get his sister back and he hoped the students would chose a different path.
He reiterated the need to speak out as soon as possible.
"With modern technology we might not talk to each other as much as we should. Let's try and change it, let's be proud of ourselves.
"We have to try and help each other out and just be a mate to your friends."
White ribbon ambassador Phil Paikea was there to support the couple and told those gathered that "silence was the killer".
"Speak up about it you could save someone," he said.
Following the powerful presentation performing arts student Shae'tel Castle said she was inspired and had found the hour "an eye-opener".
"It's opened up my mind to people doing that sort of stuff to others. Like they said it might not be easy to talk about but if we see we have to."
Fellow student Mystee Opai agreed domestic violence was a big topic.
"You have to be the better person. If you see something happening you have to get it out in the open."
The McGraths hope to speak more frequently to students and groups in a bid to spread the message it's okay to ask for help.
>If you are worried about someone or need help, call the Family Violence Information Line on 0800 456 450.