Indy Lee Henderson, from the western Sydney suburb of Airds, died on Saturday evening when a group of children were playing on a war memorial out the front of the Black Head Bowling at Hallidays Point, between Forster and Taree on the NSW Mid North Coast.

Police said Indy Lee was standing behind the stone slab as another girl was playing on top of it. The extra weight may have caused it to keel over and crush her.

Neighbour Julee Krapljanov described her as a "gorgeous girl" who will be "missed by many".

She said her mother was "mum of the year material" and would not have taken her eye off her daughter for a moment.

"I haven't met a more loving and family orientated and devoted mother," she said.

Another friend said it was a "life-altering freak accident that has just destroyed many people's lives including all of the poor little girls siblings".

Friends have set up a fundraiser to help the Sydney family.

Indy Lee's mother was among many people who rushed out of the bowling club and tried to lift the slab when children, including her siblings, started screaming.

The adults had gathered at the bowling club on Saturday night for a 50th birthday.

Superintendent Peter Thurtell told the ABC that a group of children of those adults at the party were out playing near a war memorial out the front of the club.

"The deceased child was not climbing on top of the war memorial. Another child was climbing on top of the war memorial and it appears as though the weight of that child brought it down and another girl was standing behind that slab," Superintendent Thurtell said.

"We can't speculate as to why it fell over … it appears weight was an influencing factor."

Police said emergency services were called to the club about 7.20pm.

The girl was taken to Manning Rural Referral Hospital but died from her injuries.

Mick Styles, who has a holiday van in the area, said he arrived at the club after the monument had fallen on the girl. Mr Styles, a mines rescue volunteer, helped perform CPR and assisted paramedics after they arrived.

"Everyone could see what was going on," Mr Styles said. "There were a lot of family members there, there were people there collapsed, there were children crying," he said.

"There was panic everywhere."

Mr Styles said the fallen monument was made of sandstone, and was about a square metre in size and six inches thick.

A report is being prepared for the coroner.