Gossip Girl star Leighton Meester wants full custody of her younger brother because she believes their mother isn't prioritising his welfare.
Leighton, 25, sent $7,500 each month to Constance Meester, to help pay for her illness-plagued brother's ongoing medical treatment.
But in a lawsuit filed last week, the Texan-born beauty asserted that the money was spent on cosmetic surgery for her mother instead.
And now she wants to removed Alexander from her mother's care in California, so he can live with her permanently in New York.
'Leighton is disgusted by her mother and is determined to get her brother Lex out of that situation,' an insider told RadarOnline.com.
'She wants Lex to leave their mom's California home and come to live with her in New York.'
According to the lawsuit, the website continues, Leighton provided her mother and brother with money out of the goodness of her heart, but she's now tired of her mother's lifestyle.
Leighton's younger brother, Alexander, has suffered myriad health problems, including recent brain surgery, according to the July 22 suit.
'Although [Constance] is healthy and physically able to work, Constance refuses to do so. Instead, Constance expects her daughter [Leighton] to support her financially,' it states.
'Leighton is really close to her brother, so she just hates that she can't be there to help him more,' the source continued.
It's turning into a dirty fight between the young actress and the mother who gave birth her in jail after a drug smuggling conviction.
Yesterday Constance issued a counter-attack upon her successful daughter by insisting that she had assaulted her.
Constance claims that the star threw her to the ground and repeatedly 'hit her with a bottle' during an altercation on December 11 last year.
Her suit, which was filed in L.A. County Superior Court, states that Alexander was forced to intervene to break up the fight, according to TMZ.
They also reported that Constance, used the monthly allowance from Leighton money for Botox, hair extensions, plastic surgery and other personal expenses.
Constance claims that she and her daughter had a verbal contract in which Leighton promised to give her mother $10,000 a month for the rest of her life.
The unemployed 55-year-old plans to sue Leighton for $3 million is the actress refuses to pay her the money.
According to TMZ, Leighton has asked a judge to rule that there is no such contract between them.
Earlier this year, Constance was issued a restraining order after making death threats against a Californian woman and her young son.
She allegedly threatened to 'hunt down and kill' Laurel Wigg and her son, according to legal documents, during an altercation on January 21.
Court documents filed with the Los Angeles Superior Court claim that Leighton's mother - who was also her manager - 'is a drug addict and made a threat to kill us.'
In an interview with Grazia magazine last year, Leighton stood by her mother, who she called 'an inspiratio.'
'My mother Connie inspires me. She's an amazing woman,' she said. '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.'