Emergency crews rushed to her bungalow in Dundee after the alarm was raised just before 9am on Wednesday.
Cops probing the incident later arrested a man of 32.
Wheelchair-bound Sandra, who lives alone, is receiving treatment at Ninewells in the city.
Residents in her quiet housing association development told of their shock at her injury.
One said: “Sandra is severely disabled and struggles to talk. I think she had suffered a stroke.
“You’d see her sitting at her window and she waves when anyone walks past, but she rarely goes out.
“I can’t believe this has happened here.”
Another neighbour said: “She has carers who come and go but that is about it.”
A third added she was “well-known” in the area.
Detective Inspector Tom Leonard confirmed the woman was being treated for a “severe injury”.
He added: “We received 2a call of concern for a woman. A 32-year-old man has been arrested in connection with the incident.
“I would like to reassure the public that there is no wider threat. Our enquiries are at an early stage.”
A Scottish Ambulance Service spokeswoman said: “A female patient was taken to Ninewells Hospital.”