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 her doctor, Miller is suffering from severe back pain. She had also stopped taking her medication for a thyroid condition, and that made her sick.
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.
"[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."