Barbara Coombes beat her 87-year-old father, Kenneth Coombes, with a shovel after finding the box of photographs, Manchester Crown Court was told.
The 63-year-old pleaded guilty to manslaughter by reason of diminished responsibility, saying she felt a “black cloud” over her when she attacked Mr Coombes.
Coombes had suffered 40 years of physical and verbal abuse at the hands of her “formidable” ex-military father, the court was told.
The mother-of-one had been digging in the garden and had a shovel in her hand when she “snapped”.
She walked into the living room at the family home and hit him over the back of the head with the shovel, before hitting him a second time and slashing his throat with the tool.
She then wrapped him in a carpet and put him in the garden. The following day she ordered a ton of soil and buried him.
Kenneth Coombes’ remains were found in January at an address in Reddish, Greater Manchester.
The court heard Coombes had killed her father in 2006 and concealed his body until 7 January this year, when she walked into a local police station and confessed to officers.
She continued to cover up her father’s death for 12 years, until suspicions were raised by housing officials.
She also claimed his pension and benefits on his behalf, receiving £189,125 over the 12 years.
Coombes told relatives that her father had died from a heart attack but that he would not have wanted a funeral as he “didn’t want a fuss”.
When a “winter welfare” visit was arranged by the housing association at their home, she told a housing officer that her father was away at a “Buddhist convention”.
The day before another visit from the housing officer in January, Coombes turned herself in at Cheadle Heath police station.
Prosecutors accepted she had been suffering from post-traumatic stress disorder and a severe depressive illness which “substantially impaired” her responsibility.
On Wednesday, Coombes also admitted preventing a decent burial and fraud.
Mr Justice Timothy King, who passed sentence, told her: “I accept the effect of the abuse over the years on you has been devastating.
“The history of abuse may explain but not justify the taking of life.
“Some members of the public may think the sentence wholly inadequate given what you did. Others may say it is far too much given the history of abuse.
“I have no doubt it is an appropriate sentence.”
Martin Heslop QC, defending, said Coombes was “treated as a slave and controlled by her father” and had “no one to talk to”.
Senior investigating officer Duncan Thorpe, of Greater Manchester Police, said: “Despite having years to tell someone what really happened, she only came forward when she had no other choice.
“The impact on the family and friends of all concerned cannot be underestimated.”