The 25-year-old star is suing her mother for allegedly spending money that she had been sending to help her brother with medical issues on herself. The suit—originally obtained by TMZ—claims that Meester's mother Constance had been using the $7,500 Leighton would send each month for her brother, Alexander, for cosmetic procedures and personal expenses. "This whole thing's been really tough on Leighton," an insider told People magazine. "Her only concern has always been taking care of her brother." Leighton's lawsuit also alleges that her mother threatened to sue her for $3 million if she didn't raise her monthly allowance to $10,000. Constance filed a countersuit, in which she claims Leighton broke financial promises and assaulted her in December “by throwing her to the ground and repeatedly hitting her with a bottle,” the legal papers, obtained by TMZ, say. Constance also alleges that her daughter did not uphold an agreement to support her after she couldn't convince Alexander to move to New York after brain surgery. "Since Alexander receives 24 hour care from Constance, no alternative source of income is possible," Constance's counter-suit claims. "As a direct result of Leighton's breach, there are no funds to feed and care for Alexander." This isn't the first time Meester's mother has had legal issues—she was convicted of smuggling marijuana in the 1980s and gave birth to Leighton while in a Texas halfway house. In 2008, Leighton defended her mother's past, telling Us Weekly, "She's always there for me no matter what."