Thanks for posting your query
Your daughter hits her back and hips and after that you felt that her bottom seems to sticky out.
It seems to be soft tissue injury
or a fracture
in her tail bone , if swelling is present & tender to touch.
In ritz syndrome also some spinal deformity
present like scoliosis
, so there might be some deformity of tail bone present.
Exam. of tail bone is required and x-ray is needed to reach the diagnosis.