Perimenopause ovary pain

My sister has been experiencing a sharp pain in her right ovary area that comes and goes in episodes for over three years now. She saw a doctor at the start and had a CA125 test, which was clear, and a scan that was also fine. They told her it was IBS.

Over the last month, the pain has been there most days. It feels like a sharp stabbing pain and hurts more when she sits or walks. She also has mild lower back ache. She’s now thinking it might be more peri-related. Has anyone had a similar experience?