Anne Brown body was recovered from Clerkland Burn in Ayrshire in October last year. The 51-year-old had been beaten to death.
At the High Court in Glasgow Lisa Brown was found guilty of murder, and John Wilson were found guilty of the lesser of culpable homicide.
Both were found guilty of concealing former nurse agency.
The couple had both been charged with the murder of Anne Brown and had both lodged special defense, blaming each other.
During a six-week trial before Judge Lord Matthews, Wilson had admitted helping to break Anne Brown body and throw it in a burner.
The jury of six women and nine men heard from more than 50 witnesses over 19 days of proof.
Anne Brown mother reported her and her 20-month-old granddaughter missing, 22 October 2008.
The little child was traced safe and well to Lisa Brown and John Wilson's flat in Mary Hill in Glasgow days later.
When a car found abandoned at Connaught Farm in Ayrshire was related to Anne Brown's disappearance police search was stepped up.
Her body was recovered from Clerkland Burn 24 October.
She had switched to the dead then wrapped in a sleeping bag weighed down with bricks and stones.