"She always had a positive attitude. She never let herself down," Burgos said. "And, at that moment when I spoke to her, I really felt that her hopes were running out."
According to court filings obtained by TMZ, Monica Beresford-Redman's sister Carla Burgos claims the children were told gruesome details about an accident that never happened.
Bruce Beresford-Redman's mother Juanita told the children, TMZ says Burgos claimed in the legal documents, that "their mother had been hit by a car, fell, and hit her head."
"She further told the children that no one in Mexico knew their mother, so no one could find her until their father finally found her in the hospital," the filing said, according to TMZ, "and at the time she was already dead."
An ABC News camera last week recorded Beresford-Redman driving into the garage of the home he once shared with his wife for the first time since she died.
When asked how he was holding up, Beresford-Redman replied, "I don't even know how to answer that question."
He was seen pitching a tent in the backyard while the couple's two young children watched.
His attorneys have said he left to avoid spending months, if not years, in jail while Mexican authorities build their case. He has yet to be charged with any crimes, but Mexican authorities have named him as a person of interest in his wife's death.
An attorney for Monica Beresford-Redman's sisters issued a statement saying, "the family is in shock."
"We plead that if he intends to run again that he not involve the children," the statement read.
Jeane Burgos, now back in Los Angeles, told ABC News while she was in Cancun that "there is a part of me that was sorry I wasn't able to be there for her, to save her.
"But I want her to know," she said, "we are going to do everything, everything that it takes."