@mamm. Hi there, I also wondered what other issues your sister is having. I had a total hip replacement in 2016...after a fall and subsequent failed fixation. I developed an antalgic gait afterwards. I went for a 2nd opinion a few weeks ag and was told that i likely have a neuroma from cutting through a nerve during surgery. This has left me with groin pain, pain in my buttock and a loping gait. I would suggest that your sister ask her surgeon for a CT scan and blood work, including a CRP to look for inflammation. I probably haven't helped you much but wish you and your sister well.