She was NOT in the choir for "The Perfect Fan" on The Backstreet Boys' third album "Millennium", released in midday 1999 (This is stated on the Official Backstreet Band site, www.bsbband.com, in FAQ 15)
The Leslie Carter in the choir is an old High School friend of Brian

Leslie signed a record deal with DreamWorks just six months after the Carters moved to LA (1999)

Her debut single is "I Want To Hear It From You" (June, 2000)
The B-side "True" is (co-)written by Nick Carter

I *think* her album will be called "The Weaving Of A Dream"
(Her website used to have, "Leslie Carter - The Weaving Of A Dream" as a headliner)

Billy Chapin (former member of the Backstreet Band) is producing the album
& big brother Nick has written 3 songs on it :-)

Leslie will be on Nickelodeon's "All That" Music & More Tour this summer (2000)

Little Haven http://www.littlehaven.cjb.net