As the intruders rifled through a cupboard, the 79-year-old woman screamed at them: “What are you doing?” before pressing her panic alarm button to summon help.
The three teenage raiders got away with £5,560 of property, including treasured jewellery, an i-Pad, alcohol and keys.
The pensioner’s home on East Beach had been targeted in a break-in a couple of months previously.
Two 17-year-old boys and a 17-year-old girl, all from Blackpool, who cannot be identified for legal reasons, all pleaded guilty to burglary.
One of the 17-year-old boys, a college student, who was described as having numerous previous convictions for house burglary, was remanded in youth custody to appear at Preston Crown Court for sentence by a judge on January 2 by Blackpool magistrates.
The other boy and the girl, who both had no previous convictions, were bailed for sentence at Blackpool Youth Court.
Jim Mowbray, prosecuting, said the woman, who lived alone in her Lytham home, woke to see two figures in dark clothing, looking into a cupboard, at the bottom of her bed at about 4.20am on Sunday, December 7.
She shouted at them and pressed an alarm which was responded to by neighbours and police.
Mr Mowbray added: “The victim had locked-up her home.
“She was particularly vigilant about security having been burgled several months previously.”
Steven Townley, defending, the teenage boy who was sent to crown court for sentence, said his client was adamant he had not gone into the pensioner’s bedroom. He had pleaded guilty to the offence of burglary immediately.