"She thought she would become the next famous Carter sibling," says a source who once managed one of her famous brothers.
In Leslie's case, although signed to DreamWorks Records (which released her single from the Shrek 3 soundtrack), pop stardom eluded the 25-year-old, who died Tuesday after an apparent overdose.
Instead of Leslie, after older brother Nick Carter hit it big as a member of the Backstreet Boys, another Carter sibling became famous – younger brother Aaron.
"She was always happy for her brothers, don't get me wrong," says the source. "But it was tough for her."
According to sources close to the family, Leslie remained supportive of her brothers. At various family events, she would appear alongside them, and when all five Carter siblings signed on for the E! reality show House of Carters, Leslie was an enthusiastic participant.
"She really loved the attention," says the source.
But there were dark shadows behind the limelight. According to a recently released police report, Leslie's stepmother, Ginger, stated that Leslie "had a long history of mental illness and was on medication for her depression."
Frenetic FamilyLife in the Carter family was nearly always chaotic. In 2003, Aaron Carter filed for legal emancipation from his mother, Jane Carter, after accusing her of mismanaging his money.
The next year, Jane Carter was arrested and charged with battery in an alleged attack on her estranged husband's girlfriend, Ginger Elrod.
In 2005, big brother Nick was arrested for DUI in Southern California. And in 2008, then 20-year-old Aaron Carter was charged with marijuana possession after a traffic stop in Texas.
"This is a family who has had a lot of problems," says the source. "At any given time, I didn't know who was speaking to who, who was in trouble, who was clean."
Sources close to the Carters say that the tragedy has hit the family hard. Just hours after Leslie's death, Aaron Carter posted on her Facebook page, "RIP my dearest sister. I love u."