“Since Wednesday, life has been upended,” Upadhyay told BBC Radio Wales Breakfast on Tuesday.
“For the first few days, we were we were waiting very hopefully for some information. There was some hope that he would somehow have walked up to higher ground and would have made the long trek, sort of the 60-mile trek home.
“But as the days passed, that hope has definitely faded.”
Authorities said rescue efforts had been largely focussed on the Trishuli 3A and 3B sites – hydropower projects with tunnels.
Nepali authorities are blasting into hillsides to try and reach those trapped, with a controlled blast carried out at the Trishuli site in an attempt to open up access in the early hours of Monday.
“It has been extremely difficult to reach the site. What we understand is that all the buildings are under meters of mud and it has been impossible to search for anyone there,” Upadhyay told BBC Radio Cymru’s Bwrw Golwg programme on Sunday.
“Within 20 minutes the connections were all down. The phone signals have not been working and that is why it has been so difficult to hear anything.
“It took about three days for us to get any information. We have been looking at the news, trying local contacts and trying to see what the army and the police have been doing.”
She continued: “We know that the only way to reach the site is by helicopter. You need special skills to be able to drive a helicopter in that area. It is an extremely difficult place. We have been waiting for special machines to be able to work through the mud.
“There is some good news from other stations along the river as some people were able to hide in tunnels within the hydropower stations .
“There’s not a lot of hope for that particular site – but we don’t know until someone can get in. At the moment everything is under mud.”
Upadhyay said there were about 14 hydropower stations along the river valley, and Chaudhary was a driver.
Though he was on site at the time, Upadhyay said it was unlikely he would have been deep in the tunnel network.
“So our expectation is that the first wave came and he was washed away,” she said.
