Yvonne Freaney was cleared of murder after she admitted to the manslaughter of her 11-year-old son Glen in May 2010.
The mother, of Penarth, Vale of Glamorgan, was instead given a three-year supervision order at Cardiff Crown Court. Justice Wyn Williams agreed with psychiatrists that the 50-year-old's culpability was very low and she had acted out of sheer desperation.
He agreed with the defence that sending Freaney to jail was not in her best interests, and she had effectively been in custody since her arrest more than a year ago.
After strangling her autistic son at a hotel near Cardiff Airport last May, Freaney, whose three other children are also disabled - had tried to commit suicide.
Police found Glen's body lying on a bed, dressed and tidy, with stuffed soft toys resting in his arms, in a room at the Sky Plaza Hotel in Rhoose.
Freaney was taken to hospital by ambulance with cuts to her wrists, arms and legs.