Rose West got into a slapping fight with a jail pal after claiming she had stolen chocolate from her cell.
The evil House of Horrors killer “squared up to” and “traded slaps” with the other woman as they queued to use the phone.
West, 65, has ballooned to 18 stone since starting a whole-life jail term for killing 10 victims alongside her husband Fred.
She has been diagnosed as morbidly obese and is believed to suffer from high blood pressure after gorging on chocs, cakes and other treats.
A source said of the bust-up at Low Newton jail, Co Durham: “It happened earlier this month.
“They squared up during association after Rose accused a friend of pinching chocolate from her cell.
“They traded slaps before it was broken up.”
West and the other woman were said have become close friends, passing time in each other’s cells.
West is also said have items delivered to the jail from Argos and has developed a liking for Avon beauty products.
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She and husband Fred, who committed suicide in 1995 before he could be tried, abducted, raped and tortured women and young girls including their daughter Heather 16.
Some of the bodies were buried under the cellar of their “House of Horrors” home at 25 Cromwell Street, Gloucester.
West has denied taking part in the murders but hinted she might be willing to come clean if considered for parole.
