Louise Porton denied killing three-year-old Lexi Draper and 17-month-old Scarlett Vaughan, who died 18 days apart last year.
But the 23-year-old, of Skiddaw, Rugby, was found guilty of their murder and on Friday she was jailed for a minimum of 32 years.
During her trial, jurors heard Porton did not seem distressed by the deaths.
Passing sentence at Birmingham Crown Court, Mrs Justice Yip described the murders as “evil” and “calculated”.
“These were blameless young children who were plainly vulnerable and ought to have been able to rely on their mother to protect and nurture them,” she said.
“Instead you took their young lives away.”
She added: “One way or another you squeezed the life out of each of your daughters, only calling the emergency services when you knew they were dead.
“I am sure at the time of the deaths, you intended to kill each of your daughters.
“Why you did so, only you will know.”
Jurors heard Porton accepted 41 friend requests on a dating app just a day after Lexi died, and was described by prosecutors as being “calm and emotionless” following Scarlett’s death.
Lexi Draper and Scarlett Vaughan died within days of each other
While Lexi was ill in hospital, just over a week before she died, Porton took topless photos in the toilets and was arranging to perform sex acts for money with a man she had met through a website, the court was told.
Warwickshire Police said it was also “clear from the evidence” that Porton had tried to kill her three-year-old twice before, in early January 2018, before eventually succeeding.
Porton, who described herself as a “model”, also used her Google account to search for “Why did my 3 year(-old) stop breathing” and “How long after drowning can someone be resuscitated?”
“Why did Louise do something so evil to our beautiful daughters? You are their mother, the person supposed to care for them, protect and love them.
“They were just an inconvenience to you; how could you do this?”
“I sit and think day and night and I can’t understand why my two little girls were taken away because Louise wanted to sleep around.”
He added: “I hate Louise. No punishment will ever be enough as I will never get my daughters back.”
The first day of the trial was told that from August 2016 until early November 2017, Porton lived at an address in Willenhall, near Walsall, where her landlady spent “more and more time” caring for Lexi and Scarlett while their mother was “doing social things” instead of looking after them.
Det Supt Pete Hill, from Warwickshire Police, added: “These were premeditated murders for which she has shown no remorse, and the length of the sentence reflects this.”
Warwickshire County Council and the Warwickshire Safeguarding Board confirmed a serious case review had been commissioned following the deaths of Lexi and Scarlett.
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