Complex sentence: Sebert checked into a Lemont, Illinois rehab in January 2014, claiming that she had post-traumatic stress disorder from the trauma of Kesha being attacked by her record label and Dr. Luke.
Split into simpler sentences: Sebert checked into a Lemont, Illinois, rehab in January 2014. She claimed that she had post-traumatic stress disorder from the trauma of Kesha being attacked by her record label, and Dr. Luke.