Her daughter Sarah, 22, had been cleared earlier, on the order of Judge Henry Pownall, of taking part in plotting his murder.
But both women were convicted by the jury of conspiring to pervert the course of public justice by concealing and destroying evidence of the killing.
The judge postponed sentence for reports and gave the women bail. But he warned them: 'Neither of you should read into that what the end result might be.'
As the women, from Thornton Heath, south London, who had denied charges of conspiring to murder and perverting the course of public justice, prepared to leave the dock, Mr White's mother, Anne, shouted: 'Where is the justice in this court?'
Mr White's body was found floating on the Grand Union Canal in Harlesden, north-west London, last May - four months after he disappeared.
The court was told that the 15-stone weight trainer had 'behaved like an animal' towards Linda Bowman. He had been continuing a relationship with Sarah Bowman, who had a baby by him when she was 15, when the affair with her mother began.
According to evidence, Linda Bowman had agreed to three-in-a-bed sex sessions. After one he had beaten her with a belt.Reuse content