Constance Meester had claimed the pair had an oral contract guaranteeing Leighton would pay her $10,000 a month after the 'Gossip Girl' star filed papers in July claiming the $7,500 she sent home each month to help care for her younger brother was misused by her mother for personal reasons such as cosmetic surgeries.
Although Constance - who gave birth to Leighton while serving time in Fort Worth Prison, Texas, for her role in a drug smuggling ring - countersued for $3 million in damages, a judge made an order striking her answer to the lawsuit last Wednesday (07.12.11) and as a result, gave the actress the right to obtain a default judgement.
Leighton's attorney James Spertus confirmed his client will still seek a ruling stating that she does not owe her mother parental support.
He said: "Leighton is still seeking declaratory relief from the court, which we hope to have wrapped up in the very near future."
Leighton is also said to be seeking custody of her 17-year-old brother Alexander, who has suffered health problems, including recently undergoing brain surgery.
A source said: "Leighton is disgusted by her mother and is determined to get her brother Lex out of that situation.
"She wants Lex to leave their mom's California home and come to live with her in New York."