"Then he proposed to me a couple of months after."
Miss Oliver said it hurt when people told her it was just "young love" and she would "get over it".
"It makes me angry, and sad. They don't know," she said.
Mr Heyne moved to New Zealand with his parents nearly six years ago but he was kicked out of home last year and ended up living with Miss Oliver and her family.
Having fallen in love, Mr Heyne approached his parents for help to stay.
"He kept asking for his birth certificate, passport and that, so we could get on to immigration, so we could get sorted," Miss Oliver said.
"His parents told us they already applied for citizenship, so we thought it would be fine, so we didn't worry about it.
"Then immigration turned up at the door with two police officers and they took Dennis away."
The memory of that day still haunted Miss Oliver, who wiped away fresh tears as she explained her fiance hadn't done anything wrong.
Miss Oliver's mother, Michelle, said her daughter had cried "pretty much every day" since Mr Heyne was deported.
She described him as "one of the family" and said people had no right to judge the couple's love for each other based on their age.
"My husband and I were 18 when we married and we've been together for 30-odd years. You know when you love someone ..."
Friends and family had supported Miss Oliver and were trying to raise enough money to reunite her with Mr Heyne in Germany. However, after a death in the family and helping fund a $3800 funeral, Miss Oliver now faced an uphill battle to get there.
She had planned to fly to Germany, marry and live with Mr Heyne for at least two years before returning to New Zealand together.
"I'm not going to let anything stop me," she said.
A Facebook page entitled Please Help Kayla Get to Germany has been set up.
