Maud Howard, 34, died of her injuries four days later, local historian Mike Covell said.
Mr Covell came across the death notice which said Mrs Howard had been "killed by enemy action" when he was researching his latest book The Last Raid.
Although there were a number of civilian deaths in London following the Luftwaffe raid on Hull on March 17 1945, they were all victims of unmanned V-1 flying bombs.
Until now the death toll from the so-called last raid by a lone raider which dropped fragmentation bombs down Holderness Road has stood at 12.
Mr Covell said Mrs Howard, who was resting in her bedroom in her home on Sherburn Street, off Holderness Road, with her twin sons Joseph and Thomas when the bombs started to drop, was actually the 13th and final victim.
"She grabbed the boys and ran for the door when it exploded, she was pinned behind the door.
"Her 12-year-old Margaret ran into the bedroom and found her, she was still carrying the boys. She made the ultimate sacrifice as a mum for her babies."
Mr Covell said he would like a plaque on the Boyes store which commemorates the dead and injured to be altered to include Mrs Howard - whose family every year following her death held a memorial and celebrated her birthday.
"The ultimate goal is to have all 13 victims named. At the moment it just says 'on and around the site 12 were killed and 22 injured'. Even that's wrong - 26 were injured."
During the war Hull was one of the most heavily bombed cities in the UK.
Air raids went on longer there than any other city, even after the opening of the Russian front.
Wartime Home Secretary Herbert Morrison wrote in his memoirs: “In my experience the town that suffered most was Kingston-upon-Hull.”