Polly Chowdhury, 35, and Kiki Muddar, 43 - both British Asian - were on trial with the murder of Ayesha Ali, daughter of Chowdhury, who was found half-naked with more than 50 injuries in the womens' home here in August 2013.
The girl had extensive bruising to her face, body and limbs, carpet burns suggesting she had been dragged and a bite mark on her right shoulder, the Old Bailey court here was told.
Muddar had created a cyber-fantasy world to manipulate Chowdhury through a series of fictitious friends on social media.
The couple created characters called Jimmy Chowdhury and Skyman to "facilitate a sexual relationship".
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Muddar told Chowdhury that Ayesha was "evil" and bombarded her with more than 40,000 texts which said: "You have no right to ever love or like your evil daughter.
Among the thousands of texts exchanged between the couple were messages such as "You have no right to ever love or like your evil daughter", the jury was told.
Post-mortem examinations revealed Ayesha died as a result of damage to the head from a blow or blows.
"The manipulation and hatred directed towards Ayesha led to her being beaten and tormented for a number of months," said Chief Crown Prosecutor from the UK's Crown Prosecution Service Baljit Ubhey in a statement.
"The evidence showed that Ayesha was scared and intimidated in her own home. Chowdhury and Muddar have now been brought to justice for this despicable crime," the jury was told.
The pair are due to be sentenced on Friday.