Liebert grew up on Long Island in New York. She attended Marist College in Poughkeepsie where she earned a bachelors degree in business and finance. She was hired by Dun & Bradstreet, but left, unhappy with corporate life. Successful stock investments allowed her to quit her job and travel the country.
Liebert started her professional poker career as a prop player in Colorado. She would later go on to enter tournaments and she won the first Party Poker Million event in 2002, the first limit poker tournament with a $1 million prize. She has made several final tables of the World Poker Tour (WPT), including a third place finish in the 2005 Borgata Poker Open, making her the highest finishing woman on the WPT until a runner-up finish by J. J. Liu in 2007.
At the 2004 World Series of Poker, Liebert won a gold bracelet in a $1,500 limit Texas hold 'em Shootout event. She was one of three women (Cyndy Violette and Annie Duke being the other two) to win an open event in that year's WSOP.
Liebert also appeared on and won the series Poker Royale: Battle of the Sexes.
After being eliminated from the World Speed Poker Open in London in September 2005, Kathy provided commentary on the final alongside Gary Jones.
On June 1, Liebert made the Final Table of the $10,000 Pot-Limit Hold'em World Championship at the 2008 World Series of Poker and finished in 3rd place, earning $306,064.
Although Liebert has made a career out of poker, she still uses her financial acumen to invest in the stock market. She also holds a blue belt in karate.
Liebert now resides in Las Vegas, Nevada and Downey, California.
As of 2008, she has one World Series of Poker (WSOP) bracelet and her total live tournament winnings exceed $4,800,000. She has won more prize money in open field tournaments than any other woman in poker history and is ranked 39th overall.