We did know she was being bullied but she led us to believe that she was coping better with it.

Victim's sister Sarahjane

Last Saturday, Denise told her mother she was going to lie down for a rest in bed. However, she took an overdose and died.

Her sister Sarahjane told the Belfast-based newspaper, Sunday Life: "We did know she was being bullied but she led us to believe that she was coping better with it.

"We had no idea she was in such despair. I don't know how we're going to cope."

But she said that the family did not blame anyone for Denise's death.

"I'm angry that Denise has gone but I'm not blaming anyone," she said.

Hundreds of calls

Sarahjane said her parents Marta and Stuart and her brother, also called Stuart, were devastated by the tragedy.

The director of children's charity Childline, Delia van der Lenden, said the organisation dealt with several hundred calls a year about bullying.

Speaking on BBC Radio Ulster, she said children often called the organisation "in deep distress, feeling they have no room to turn, feeling they cannot talk about it and feeling that if they do talk about it that it might get worse."

Delia van der Lenden: Young people can be scared to talk

She added: "This is why we feel that the Childline Confidential Helpline service provides an outlet for young people who are just too scared to talk to anyone else about bullying."

The Childline number is 0800 1111.

Despite the tragedy, teachers at the Belfast Model School for Girls recently won an award for their work in combating bullying.

Staff had worked extensively with Denise and her family to try to ease the situation.

Acting principal at the Belfast Model School for Girls Vivienne Boyle paid tribute to Denise.

She said: "Denise was always a popular girl, who had a lot of good friends, and she was a good friend to them.

They often call us in deep distress, feeling they have no room to turn

Delia van der Lenden

"Staff and pupils are very, very sad about her death. Our thoughts are with her family and we will be doing everything we can to support them."

The sorrow of the community at Denise's death was reflected in the massive attendance at her funeral last Wednesday and in the dozens of moving newspaper tributes.

Her family have now called on the government to set up a community programme to tackle bullying.

"It's too late for Denise, but for the sake of other young people and children something needs to be done, " Sarahjane said.