Gabrielle's sister Alana Koornneef said the council had been "really good" to deal with.
"There were two options [for a seat location] but this area was perfect.
"Both my sisters [Kellie and Gabrielle] and I went to Raumati Beach School and it's just such a nice spot.
"We came and saw it with a woman from the council and this was the only option for this area, and we liked it."
Alana said the seat, which has a rose garden close to it, "was such a good tribute to Gabrielle".
"She would really appreciate it.
"And we've got a place to come."
Alana said, "We would like to thank everyone who has been involved in this project from the people who donated money and the council."
A plaque in the middle of the seat said: In loving memory of Gabrielle Koornneef. A life that touches others goes on forever.