Orobator's mother said she has been denied access to her daughter since her arrest.
"She is not alone," she said. "We love her. We can't wait for her to come back home."
Orobator's mother said she last spoke with her daughter, the oldest of four children, in July.
"She was very happy ... and chatty," her mother said, adding this was the first time the young woman had traveled outside the United Kingdom and Ireland since they lived in Nigeria during her childhood years.
Reports from former inmates at Phongthong prison say conditions there are dire.
"That prison is notoriously difficult in terms of conditions," Reprive's Oshea said. "There have been reports of abuse and even one death in that prison."
Reprieve's primary concerns are for a fair trial and for Orobator's health, Oshea said.
"For the last 72 hours, she's been facing the prospect of going on trial in a foreign country, where she doesn't speak the language and doesn't know the law, without any kind of legal representation -- and on trial for her life," she said.
According to the human rights group, there was a chance the government of Laos would consider a prisoner transfer agreement with the United Kingdom if the U.K. government agrees.
"That could benefit Samantha if she is convicted," Oshea said. "What we're primarily concerned with now is that she gets a fair trial, and the worry is that she's not going to get one. If she does have an innocence claim here, it deserves a hearing."