Lorraine Thorpe, now 16, of Clapgate Lane in Ipswich, was found guilty in August of murdering her father Desmond Thorpe and a woman called Rosalyn Hunt.
Thorpe, 15 when the murders took place in 2009, was told at the Old Bailey she would serve at least 14 years.
Paul Clarke, 41, also convicted of two murders at Ipswich Crown Court, was sentenced at an earlier hearing.
Clarke, of Mountbatten Court, was also jailed for life and told he must serve a minimum of 27 years.
Mr Justice Saunders said Thorpe could be “manipulative” and was not acting entirely under Clarke’s control, adding: “She found violence funny and entertaining.”
The bodies of Ms Hunt and Mr Thorpe were found at separate addresses in Ipswich in August 2009.
Both Clarke and Thorpe had denied the charges and gave no evidence during their trial.
They had repeatedly beaten and tortured Ms Hunt and then smothered Mr Thorpe to death.
The judge said: “Far from being sorry, Lorraine appears to have gloried in it, describing to her friends at one stage how she stamped on Rosalyn’s head.”