@Mrs Winslow - Yes, juvenile rheumatoid arthritis is an autoimmune disease. I have a cousin who has it, too. He's in his 20s now and his symptoms are almost gone. It sounds like your friend has a more serious case. It is not common for people with JRA to need joints replaced, but it's done if a particular joint has just been too badly damaged. Some people with JRA will get mostly better by adulthood, while others will have some pain their whole lives.
I have an interest in childbirth and C-sections, so I Googled your question about hip replacement and delivery. There are not a whole lot of women out there in that position, as you can imagine! It looks like a lot or most do have c-sections, but it's not an absolute must depending on other aspects of the person's condition.