Kate believes that if she had not been in the unit the 46-year-old might still be alive, the Daily Star reported.
Her worried husband, Prince William, is even considering quitting his RAF job early to be with her in London.
Along with family and friends, he has tried to reassure Kate the tragedy is not her fault.
Kate is also dreading having to go back to the King Edward VII hospital because of the awful events that followed her first stay.
Saldanha, 46, was duped into putting through a prank call from the two Aussie DJs pretending to be the Queen and Prince Charles.
“Kate is feeling vulnerable and the nurse’s death is a dreadful blow. She is terribly upset and blames herself. But everyone is telling her there is no need to feel guilty,” a royal aide said.
“William feels helpless. He can hold her hand and be sympathetic but Kate still thinks if she hadn’t been in that hospital none of this awful tragedy would have happened.
“It is not easy for her, especially if she has to go back into that hospital again,” the aide said.
The royal couple has been talking about whether William should leave the Forces when his tour of duty ends next year.
Now, following all the upset, rescue helicopter pilot Wills is thinking about quitting early to be with his wife.
She has been advised to stay close to her doctors in London rather than at their remote cottage near his RAF base in north Wales.
William is expected to decide by Christmas, then let his bosses know.
London: The Duchess of Cambridge is devastated and blames herself for the death of hoax call nurse Jacintha Saldanha, according to royal aides.
First Published: Sunday, December 16, 2012, 11:44