Jacqueline Petrie invited Lisa Diduca into her home in October 2014 after she saw her standing in the street crying.
Diduca then attacked her, threatened her with a pair of scissors and stole items from the house in Dundee.
The 26-year-old denied a charge of assault and robbery, but was found guilty after a trial and was jailed.
Dundee Sheriff Court heard Ms Petrie spotted Diduca crying in the street in the early hours of the morning, and went to ask her what was wrong.
The 43-year-old said she invited the younger woman into her home after "she kept saying she was scared".
She said: "I was alone in the flat at the time. All of a sudden she started attacking me.
"It came out of nowhere. She started opening drawers and taking things, then she found a pair of scissors and held them to my neck. I was scared for my life."
Diduca later told police that Ms Petrie was lying, accusing her of being drunk and having a mental disorder.
Sheriff Alastair Brown jailed Diduca for three years after a jury found her guilty.
He said: "Ms Petrie saw you upset and crying and she went to help you. She did you nothing but good, she gave you shelter in her own home.
"She was in every sense a Good Samaritan to you, and you repaid her by assaulting her in her own home. In particular you took a large pair of scissors and held them to her neck and placed her in a state of terror.
"Robbing someone at the point of a weapon will always attract a serious sentence. Nothing excuses grabbing a woman in her own home, putting scissors to her neck and robbing her."
A woman who assaulted and robbed a "Good Samaritan" who took her into her home has been jailed for three years.