The sister of a 20-year-old mother whose body was found last weekend in East Boston said Thursday night that relatives are desperately seeking to learn how their loved one died.

“It’s very hard for us to just sit there and wait,” said Ayahnna Williams, 28, of Medford.

She identified the woman found in the water Saturday morning on Constitution Beach as her sister, Treshawna Williams of Malden, who leaves a 20-month-old daughter, Taraie.

David Estrada, a Boston police spokesman, said Thursday night that he could only confirm the victim’s last name as Williams. He said officers recovered her body Saturday.

He said he did not know whether foul play is suspected, and a spokesman for Suffolk District Attorney Daniel F. Conley had no information late Thursday night on the case.

Ayahnna Williams said her sister was last seen leaving a friend’s house near Central Square in Cambridge by herself at 11:50 p.m. Friday.

Treshawna Williams had recently finished a medical administrative assistant program and had been offered a job at a Boston hospital, her sister said, and had hoped to continue her studies and eventually open a youth center.

She said police have told the family that they are waiting for information from the medical examiner’s office before they can say anything definitive about her death.

She said they told her it might take weeks.

She said that the medical examiner’s office had shown her a photograph of Treshawna that showed lumps over one eye, which she was told may have been caused by being in the water for a long time.