Rosetta West said she was anxious and in pain after falling at her sheltered flat in Poole, Dorset.
South Dorset MP Richard Drax said protocols did not allow staff to move Mrs West while they waited.
Health minister Philip Dunne said the South Western Ambulance Service had seen an 11% rise in calls this year.
Mr Drax told the House of Commons on Monday the "frail" pensioner's plight was typical of cases which were "down-graded by call handlers under immense pressure for other incidents".
Melton Court manager Fiona Smith said staff had been left "grief-stricken" by Mrs West's ordeal, which followed another recent four hour wait for an ambulance for a resident.
She said ambulance delays had reached unprecedented levels, with "excruciating" waits becoming common.
Ms Smith said: "I've been a care manager for 13 years and never had a problem... but now it's normal to wait two and a half hours."
Mrs West, a Blitz survivor, said she had put the "very, very painful" wait into perspective and did not hold any ill-feeling towards the ambulance service.
She said she had been left bed-bound since the fall in August, which may have caused a knee fracture.
Her son, Paul Coleman, said the "disgusting" delay could have been life-threatening if his mother had suffered internal damage.
The South Western Ambulance Service said Mrs West had not needed hospital treatment and it had to prioritise unconscious or non-breathing patients.
It said many domiciliary care organisations operated a 'no lift' policy, leaving patients waiting for an emergency ambulance even when there was no medical need.
The plight of a 96-year-old woman, who was left lying on the floor while she waited four hours for an ambulance, has been raised in parliament.