Arthritis. Causes heaps of pain and reduced mobility which brings a whole lot of other medical complications. Hips replacement are super common past a certain age.
Osteoarthritis (or specifically, osteoarthrosis), not rheumatoid arthritis (swelling of the areas around the joint due to immunoresponse), it's when the cartilage on the femural head wears out so its just bone on bone. Doctors can inject hyaluronic acid for temporary lubrication but a replacement is pretty much the only long term treatment.
The question (“what set of conditions actually cause a person to get a hip replacement surgery apart from an accident?”) wasn’t about her case. The article clearly indicates she had an accident (“Twenty years before, she had a hip replacement that stemmed from an injury she sustained in a car crash ten years before that”)