Three years on, she is sure she was targeted for abuse because she is a woman.
"You get abused by players, parents, everyone. They think females have no idea about sport, especially a male-dominated sport."
Some of the abuse was physically threatening. It wore her down to the point where she couldn't face it.
"There's no respect for anyone in the centre but it's most definitely a lot worse for female referees. I would have liked to have carried on but it's just not worth it."
Showing angry parents the rule book and explaining her decisions did nothing to placate them.
"It's just atrocious, I don't know how people cope."
Ms Karreman says she can't see a way to change the behaviour. Some of it is a lack of understanding of the rules and a well-meaning desire to see kids succeed.
But she says that passion goes overboard and it takes only one or two people to turn sideline support into nasty heckling. "There is passion but there is no need for the verbal diarrhoea that goes with it."
Even players seemed to buy into the attitude that women were ineffective coaches. "A new player was told when registering that he would be in my team of players from last year. The look of disgust and the attitude he showed me was unbelievable unless you saw it."
Ms Karreman is now vice-president of the football club, running administration. "Even now, I still get it. There are men walking around thinking, 'Who the frig are you?' When the grounds are closed and I walk up and say, 'Excuse me, you can't be here', I get the attitude of, 'What right have you to tell me what to do?"'
Meanwhile, an academic says New Zealanders need to take steps to improve sideline behaviour. Professor Sarah Leberman, who heads Massey University's School of Management, specialises in women in sports management.
She has done work in the US and New Zealand looking at why relatively few women are involved in coaching kids' sports teams. She has found it is due to the verbal abuse and lack of respect they get from other parents.
She said many women reported that they could put up with heckling and verbal attacks for a while but when it happened week after week, it became too much to handle. Professor Leberman said sports organisations hoped the problem would ease, but it seemed to be getting worse.
"There's no mechanism to control it because the referee or umpire is just trying to keep what's happening on court happening; they can't deal with the parents, too."
US colleagues had developed a package to help parents and coaches combat bad sideline behaviour.
Efforts to counter it needed to come from within sport, she said. "We've been quite reactive, we haven't taken the initiative, we should do something more constructive."
