The `Gossip Girl` star has reportedly initiated a lawsuit against her mum Constance Meester for using cash she had sent to her younger brother and sister for plastic surgery, hair extensions and Botox injections.
According to court documents obtained by TMZ.com, Leighton was sending her mother - who allegedly "refuses" to work - $7,500 a month so she could provide care for the 25-year-old star`s younger brother Lex, who suffers from severe medical issues.
However, rather than using the money to provide essentials for the youngster, Constance - who gave birth to Leighton while serving time in Fort Worth Prison, Texas, for her role in a drug smuggling ring - was putting the cash towards a whole host of cosmetic procedures.
Claiming the pair had an oral contract guaranteeing Leighton would pay her mother $10,000-a-month for life, Constance reportedly threatened to file a $3 million law suit against the brunette beauty unless she started handing over the cash.
With the star insisting no such conversation had been had, she is now keen for a judge to declare that there was never any contract - verbal or otherwise - between the family members.
Leighton has previously claimed her "eccentric" mother has "inspired" her throughout her life.
She said: "My mother Connie inspires me. She`s an amazing woman. When I was a kid I wanted to be an actress and she completely backed me. She is her own person, very eccentric, very individual."