Well travelled and excited and optimistic about heading to New Zealand for a six-month work contract, Miss Lam had been with 25-year-old Connor Hayes for almost two years.
A friend described the pair as a ''perfect fit''.
They had spent time in South America before coming to New Zealand.
Miss Lam had been due to start working at the radiology department at the Nelson District Health Board on Monday.
The couple were last seen at Fox Glacier on Tuesday afternoon last week, the day a wild front lashed the Haast Pass alpine area with torrential rain and gale-force winds.
Police now say it is likely the camper van in which the Canadian pair were travelling was hit by a landslip and hurled into the raging and flooded Haast River.
Mr Hayes and Miss Lam have not been seen since.
''Unfortunately, there is no sign of the couple, but we will continue searching. Things are not looking good for their survival,'' West Coast police area commander Inspector John Canning told a media conference on Tuesday.
The couple, from Ontario, were travelling from Haast towards Wanaka on State Highway 6. The accident happened sometime after 6.30pm, he said.
''We know roughly when it happened as we have spoken to a witness from Haast who was following a camper van through the Haast Pass last Tuesday and turned back because the weather was so bad,'' Insp Canning said.
He would be talking to the coroner because there had been no sign of the couple, which ''indicated they may have come to harm'', Insp Canning said.
Searchers who were scouring the river in a jet-boat on Tuesday told him that the water had been 6m higher last week during the terrible weather.
Ms Lam's brother Jeffrey listened into the media conference from Canada via telephone and afterwards thanked all the searchers for their efforts.
''Also on behalf of our family and friends, I hope and pray you find something which would be able to give our families closure,'' Mr Lam said.
Police searchers released a photo of the wrecked camper van's chassis on Tuesday.
Constable Rob Manera, of Haast, discovered the wreckage in a narrow gorge, just metres from a huge landslip at Diana Falls.
Insp Canning said contractors working on clearing the slip suggested Const Manera look in a particular area near the slip.
It was possible the camper van had been blown off the road in gusting winds, but he doubted the missing couple were buried under the slip, he said.
The ''guts'' of the camper van had been torn apart in the crash, Insp Canning said.
''All we initially found was the chassis and wheels; the rest of the rental vehicle, including the engine and gearbox, are gone.''
A fuel tank from the camper van was found on Tuesday night, washed up on the beach about 7km north of the mouth of the Haast River, more than 50km from where the vehicle left the road.
At dawn yesterday, 16 LandSAR volunteers and police officers set off on foot to scour the Haast River, as well as along the river from below the gorge.
Two jet-boats were also on the river, while a helicopter search, using three spotters, began. A police spokeswoman said aerial searchers had spotted a seat from the camper van, ''about halfway'' down the river towards its mouth.
Police had been unable to confirm whether the couple were in the vehicle when it left the road. Const Manera said he did not believe the pair had ignored any weather warning signs not to travel in the area, or road closed signs.
The New Zealand Transport Agency confirmed the pass was closed at 8pm on Tuesday last week. Const Manera said the couple would have driven into the area before the road closed signs went up. ''They would have been there lawfully and not breached any roadblocks or warnings.''
- Greymouth Star /APNZ
