I'm so sorry, I have never had an experience quite like that. To be honest I've never even heard of it. I've had a cyst on my ovary before, which ruptured and caused a great deal of pain for several hours, but that just fades and goes away. This sounds awful.
All I can say is that my sympathy goes out to your sister, and I hope that something can be done for her.
No regrets. The past makes you who you are today.