Miller was taken to the hospital from the residential re-entry center in Long Beach, California, due to a back injury, a source tells ET.
Miller has been dealing with the injury for a while, the source says, adding that she will eventually need surgery to correct the problem.
According to TMZ, who first reported on Miller's hospitalization, the 51-year-old reality star was able to walk out of the center and into the ambulance on her own.
The former Dance Moms star was released from the Federal Correctional Complex in Victorville, California, last month, after spending eight and a half months behind bars for bankruptcy fraud, and transferred to the re-entry facility for the remainder of her sentence. Miller is scheduled to be released from the halfway house on May 25.
Abby Lee Miller from 'Dance Moms'
Abby Lee Miller from 'Dance Moms'
UNIVERSAL CITY, CA - AUGUST 11: Actress Abby Lee Miller attends the Teen Choice Awards 2013 at Gibson Amphitheatre on August 11, 2013 in Universal City, California. (Photo by Jason Merritt/Getty Images)
LOS ANGELES, CA - APRIL 13: Abby Lee Miller arrives at the Logo NewNowNext Awards 2013 held at The Fonda Theatre on April 13, 2013 in Los Angeles, California. (Photo by Michael Tran/FilmMagic)
WEST HOLLYWOOD, CA - FEBRUARY 24: TV personality Abby Lee Miller attends Chopard at 21st Annual Elton John AIDS Foundation Academy Awards Viewing Party at West Hollywood Park on February 24, 2013 in West Hollywood, California. (Photo by Stefanie Keenan/Getty Images for Chopard)
SANTA MONICA, CA - MARCH 24: TV personality Abby Lee Miller attends the 3rd Annual Whispers From Children's Heats Foundation Legacy Charity Gala at Casa Del Mar on March 24, 2017 in Santa Monica, California. (Photo by Alberto E. Rodriguez/Getty Images)
LOS ANGELES, CA - MAY 14: Abby Lee Miller is seen on May 14, 2017 in Los Angeles, CA. (Photo by GP/Star Max/GC Images)
Reality TV show star Abby Lee Miller leaves at the federal courthouse after pleading not guilty to federal charges in Pittsburgh, Pennsylvania November 2, 2015. Miller pleaded not guilty in a Pennsylvania courthouse on Monday to concealing over $755,000 in income she is accused of earning while head instructor on "Dance Moms" and spinoff shows. REUTERS/Elizabeth Daley
LOS ANGELES, CA - MARCH 11: Actor Abby Lee Miller at Nickelodeon's 2017 Kids' Choice Awards at USC Galen Center on March 11, 2017 in Los Angeles, California. (Photo by Frazer Harrison/Getty Images)
SANTA MONICA, CA - MAY 30: Dance Instructor Abby Lee Miller attends the Abby Lee Dance Company LA's VIP Grand Opening at Abby Lee Dance Company LA on May 30, 2015 in Santa Monica, California. (Photo by Vincent Sandoval/WireImage)
INGLEWOOD, CA - MARCH 28: TV personality Abby Lee Miller attends Nickelodeon's 28th Annual Kids' Choice Awards held at The Forum on March 28, 2015 in Inglewood, California. (Photo by Jason Merritt/Getty Images)
INGLEWOOD, CA - MARCH 28: TV personalities/dancers JoJo Siwa, Maddie Ziegler, Kalani Hilliker, tv personality Abby Lee Miller and dancer/tv personality Mackenzie Ziegler, accept the Favorite Reality Show Award for 'Dance Moms' onsteage during Nickelodeon's 28th Annual Kids' Choice Awards held at The Forum on March 28, 2015 in Inglewood, California. (Photo by Lester Cohen/KCA2015/WireImage)
SYDNEY, AUSTRALIA - MARCH 12: Abby Lee Miller and Maddie Ziegler arrives at the 2015 ASTRA Awards at the Star on March 12, 2015 in Sydney, Australia. (Photo by Caroline McCredie/Getty Images)
CULVER CITY, CA - JUNE 14: Abby Lee Miller attends the Opening Night Party during the 2017 Los Angeles Film Festival at Culver Studios on June 14, 2017 in Culver City, California. (Photo by Kevin Winter/Getty Images)
INGLEWOOD, CA - AUGUST 24: TV personality/Choreographer Abby Lee Miller attends the 2014 MTV Video Music Awards at The Forum on August 24, 2014 in Inglewood, California. (Photo by Jeff Kravitz/FilmMagic)
NEW YORK, NY - JULY 16: (L - R) Shad Moss, Abby Lee Miller, Keshia Chante attends 106 & Park at BET studio on July 16, 2014 in New York City. (Photo by Bennett Raglin/BET/Getty Images for BET)
NEW YORK, NY - JULY 16: TV personality Abby Lee Miller visits 106 & Park at BET studio on July 16, 2014 in New York City. (Photo by Bennett Raglin/BET/Getty Images for BET)
RIDGEWOOD, NJ - JULY 15: Abby Lee Miller signs copies Of Her Book 'Everything I Learned About Life, I Learned From Dance Class' at Bookends Bookstore on July 15, 2014 in Ridgewood, New Jersey. (Photo by Jim Spellman/WireImage)
Abby Lee Miller, The FOX Teen Choice Awards 2014 arrivals (Set B) at the Shrine Auditorium in Los Angeles, California. August 10, 2014. (Pictured: Abby Lee Miller)
LOS ANGELES, CA - JULY 08: Dance Instructor Abby Lee Miller arrives at Marvel Universe LIVE! Age Of Heroes World Premiere Celebrity Red Carpet Event at Staples Center on July 8, 2017 in Los Angeles, California. (Photo by Ari Perilstein/Getty Images for Feld Entertainment)
"[She'll be] spending as much time outside of the halfway house as she can, and then she will just be coming back to sleep afterwards," Myers explained. "She most likely will not be in a cell, there are actual rooms inside the facility. Usually, the rooms have doors and depending on the situation, she can either be alone or she will have to share with some people."
"She will not be wearing an ankle bracelet or anything like that," Myers added. "When she leaves, she can go wherever, she just needs to be back by curfew, and she will definitely not want to miss that."