Gossip Girl actress Leighton Meester is suing her mom over misused money, according to a report.

The young star, took the case against her mother, Constance, for spending money on herself – money that the actress had been sending for the care of her brother Alexander, who has medical issues.

The suit alleges that her mother used over €7000 a month for cosmetic procedures, among other personal expenses.

"This whole thing's been really tough on Leighton," a source tells People. "Her only concern has always been taking care of her brother. Leighton's really close with her brother and her dad, her parents are divorced. Leighton's a sweet girl, she cares about work, friends and family."

On Monday, Constance fought back by filing a counter-suit claiming that she had sacrificed almost everything to advance her daughter's acting career, only to have Leighton break financial promises.