Her son, immediate-past Federated Farmers national president Bruce Wills, said he would go to his grave knowing he did all he could to find his mother.
The family had decided to hold the memorial after a "final push" to find Ms Wills last month, which involved a search party of more than 100 people led by internationally renowned search and rescue expert Ross Gordon.
"There does come a time where we've got to let her rest in peace and move on. [The memorial] will be a time to remember, a time to reflect. It's a bit of closure for the family."
However, he would always keep an eye out for any sign of Ms Wills.
"We'll never stop looking. I guess we'll always wonder until the mystery is solved."
The memorial service for Ms Wills will be held at Trelinnoe Gardens on Saturday, March 14 at 11am.