She said she once cried reading online comments following the publication of one of her first columns.
"It was the sheer volume and I was not used to it ... If you are having a down moment, you can read something and think 'ouch'."
Since then she had learned not to spend her days checking notifications and reading comments on Facebook and other websites - although she still regularly blocked and banned people on Twitter and Facebook and reported them.
"It can get pretty bad. I had one this weekend because I apparently wrote I liked wine and dating - even though I actually wrote I like date scones - so I am apparently putting it out there I wanted to be raped."
Marvelly said she couldn't believe the comment and wondered how on earth the writer arrived at such a conclusion.
She said she was often called names, such as a "slut" and a "whore", and most of the hateful comments centred around people insinuating she was promiscuous.
"It's not easy being an opinionated woman online," she said.
"For me I have had to learn to switch off ... A lot of these trolls are inherently sad people."
She would never let online criticisms prevent her from speaking her mind or change who she was, she said.
"I think it would be impossible for me to do that. Then you are letting other people dictate your own sense of self. That's letting them win ... A lot of it is trying to remember who you are and what you are doing."
She said cyberbullies would never approach her on the street and tell her to her face what they wrote. "But they are emboldened when they are behind a screen."
Marvelly said she was reasonably hardened to the attacks but teenagers weren't, and it "broke her heart" to think they were having to deal with the torment.
"Being a teen is hard enough. We need to remember our human decency."
She said education was the first step to reducing cyberbullying, including talking to young people about being good online citizens.
"It's not just young people, it's also adults who need to remember their manners."
For extreme cases there should be consequences, she said.
Last year's Harmful Digital Communications Act was a good start to treating the problem more seriously but it was timely now to review the Act to make sure it was doing what was intended, she said.
And her advice to cyberbully victims? "Reach out and don't bottle it up because that's when it gets worse."
