Louise Porton was found guilty on Thursday of killing three-year-old Lexi Draper and 17-month-old Scarlett Vaughan less than three weeks apart last year.
A jury at Birmingham Crown Court convicted her of both murders following a five-week trial.
Jailing Porton on Friday, Mrs Justice Yip described Porton's actions as "evil" and "calculated", telling her: "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.
"Instead you took their young lives away."
The judge 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."
Porton, who described herself to male suitors as a "model", accepted 41 friend requests on a dating app the day after Lexi's death.
She was described as "calm and emotionless" after Scarlett's death and delayed calling an ambulance for the youngster, even filling up with petrol as the toddler lay dead or dying in her car.
When 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.
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.
The judge said she was sure Porton had been responsible for events leading to Lexi's earlier admissions to hospital on January 2 and 4.
Mrs Justice Yip said: "On January 4, you left Lexi in a critical condition, her life being saved by skilled resuscitation by paramedics."
At the time, she used her Google account to search for "Why did my 3 year(-old) stop breathing", and "How long after drowning can someone be resuscitated?".
The judge added that the night Lexi was killed, Porton made further "sinister" internet searches about death.
"I am left in no doubt that you delayed calling for an ambulance until you were sure she was dead and could not be resuscitated," she said.
The 23-year-old, of Skiddaw, Rugby, Warwickshire, suffocated Lexi in the early hours of January 15 last year and was then heard "laughing" at a funeral parlour two days before killing Scarlett just over two weeks later, on February 1.
The judge added that post-mortem examinations revealed signs of previous injuries, possibly caused by Porton, while Scarlett "had signs of prior airway obstruction".
She told Porton, who had only previously been cautioned for wasting police time aged 15 before the murders, that she had carried out "the grossest abuse of trust" against her girls.
The judge said: "Those who loved Lexi and Scarlett have been left bewildered as to how and why you could have done something so evil. Your actions have devastated so many lives."
The children's father Chris Draper, who never met Scarlett, said he felt "broken", with "nothing to live for".
In a victim impact statement read to court by the prosecution, he said: "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.
"Maybe if social services had listened to me, my girls would still be alive today."
Mr Draper, who was in court for sentencing, said: "I hate Louise. No punishment will ever be enough, as I will never get my daughters back."
Porton, who sat in the dock throughout the hearing looking at her feet with her head resting on her hands, did not react.