Louise Porton, 22, of Rugby, Warwickshire, was charged today over the deaths of Lexi, three, and 16-month-old Scarlett.
Lexi was found unconscious at home on January 15 last year and pronounced dead by paramedics at the scene.
Scarlett died two weeks later on the night of February 1 after falling ill and being rushed to hospital.
Following an investigation Police a file was submitted to the Crown Prosecution Service and on Friday the decision was taken to charge Porton with murdering Lexi and Scarlett.
She will appear at Leamington Magistrates’ Court this morning.