Any advice for my sister?

[Kindofnewtothis]

Hi there, wasn't sure where to post this so I'm sorry if it's in the wrong section.
My little sister had her left ovary and fallopian tube removed when she was just 18 because there was a tumor the size of a rugby ball wrapped round it. Since then she's had the worst stomach pains and recovery etc, it's not been easy for her.
A few years later and she's had another ultrasound showing that her right ovary, her only ovary, is polycystic. Realistically could this be causing all of her excruciating pain? Our mother and I have both been diagnosed with pcos before and neither have experienced pain, but I do appreciate that everybody's different. Just keep getting the feeling that something's being missed.
Does anyone also know how this would effect her fertility in the future? I know that pcos in general can affect fertility, but the fact that there's only one ovary too, does that make it any worse???
Sorry for the long post, the doctors don't answer questions well and I thought maybe someone out there had been in a similar situation.

Ovarian cysts can grow and cause pain. I've had painful ovarian cysts which have burst with Polycystic ovaries. I'm also going to have a laparoscopy to check for endometriosis so hers could also be that (which wouldn't show up on ultrasound). Getting pregnant with endometriosis can be trickier. Your poor sister :(

It could also be scar tissue causing her pain. I would definitely get referred back to gynae if it was me (also had left ovary and tube removed due to a cysty tumour).

Hope your sister gets some answers xx

Oh and I was told having one ovary would not affect my fertility xx