A police spokesperson said she had not indicated she would be away for a long period.
Ewings had been working in Clarence. She was living only a few minutes from her work.
Ewings' Gold Coast-based grandmother, Dulcie Brumpton, told the Herald today they believed her employer was the last person to see her alive.
She said Ewings' mother, her daughter, was distraught and had hardly slept since learning of her disappearance when it was reported by her boss on Monday morning.
"She travels a lot and was working in [Clarence] ... and she absolutely loved her job, absolutely loved it. So it's just very strange that all of this has happened."
Brumpton said she last spoke to her granddaughter on Friday.
Ewings was in good spirits and was telling her about possible plans to attend a car show on Saturday with a friend from work.
Ewings lived on a property next door to her work in Clarence, she said.
"I said to her one day, 'do you live near to your work?' and she said 'yes, just five minutes'. Like, next door or the house after."
"From what we're hearing over here a lot of people had thought she had been found, but no."
Brumpton said she had been keeping in daily contact with Ewings' mother, who was concerned and desperate to find her.
"The last message I got from her was last night and she said they were bringing in more people today to look.
"I think it's very, very hard on her. I don't think she's slept since the weekend. She's just having a really, really hard time. And her other sister who's had to go back home because she's got little children."
The family had been told that Ewings had bumped into two elderly women during her walk on Sunday night.
"They said they saw her get in her car and drive home but nobody has seen her since.
"I thought she'd actually walked down ... but these ladies said they saw her drive home, so I don't know."
Ewings' car was at her home and none of her belongings were missing.
"Her handbag, her cards, everything is still on the kitchen bench where she had left them. Everything was there, nothing had been taken or moved out of the house.
"Her phone is missing but they said that she's not answering and that it would have run out of data by now."
Brumpton wasn't sure what might have happened, but knew that Ewings "walked a lot".
"All I know is that it's quite a rough area, a lot of scrub and trees and bush and the helicopter [crew] have said it's difficult to find things through all the trees so that's why they're bringing the dogs in to try and track it."
Brumpton said it was odd for Ewings not to have been in touch with anyone.
"We're starting to wonder a little bit. It's just odd for her not to have been in touch with somebody. She contacts everybody, all the family, all the time."
Ewings' was one of five siblings, she said, and part of a wider tight-knit family.
A police spokesperson today confirmed search teams from all over the South Island were in the Clarence area assisting local police with the search.
"On 20 September Melissa left an address in Clarence Valley to go for a walk. She had not indicated she would be gone for a long period."
Search teams had been searching every day since "over an extensive area around Clarence and the river".
The search would continue over the coming days, "weather permitting".
As for whether police were treating her disappearance as suspicious, the spokesperson said she was being treated "as a missing person and police are keeping an open mind as to what has happened".
The MetService is forecasting strong winds and showers for the next couple of days, and a temperature drop to 5C overnight Monday.
