Extremely painful cysts on ovaries (for a friend)

A friend of mine has recently been diagnosed with cysts on her ovaries after YEARS of extreme pain. How nobody picked it up earlier is beyond me. She would be vomiting and shaking because of the pain and everybody just kept telling her there was nothing there etc etc. She is waiting for surgery. I have some questions:

She doesn't have children yet, how does this surgery affect fertility?
She has also been on BC to try and stop the pain (about 3 months) I would have thought BC would stop the follicles growing and stop the cysts from appearing??

I don't understand how this has never showed up on any scan she has had done before. I suggested pcos or edometreosis in early days because i knew something was wrong, but specialists and Gp's have all told her they can't find anything wrong until recently. Surely vomiting and shaking from pain every time you have a period is not normal!? Very annoyed she has been brushed off for so many years and had to put up wit this.

If the pain is just with her period, I would say it's an endometrioma (chocolate cyst) not a regular cyst as they are not specifically cyclic as far as I am aware. I have had a large endometrioma on my left ovary. They are painful during your period because you bleed into it and it gets larger, also the blood that's unable to escape contributes to the pain. Regular cysts normally are painful until they burst, so not just during your period.
If it's normal cysts then I would guess that it's a reoccuring thing, not the same cyst over such a long period of time. And yes, BC would stop the cysts appearing if they are follicle cysts, but like I said I would put money on it being endo related.
As far as fertility goes, the doctor sucessfully drained my cyst without harming the ovary. I know I ovulate out of it as I can feel the pain on that side sometimes.

ETA why they haven't been picked up, well endo is hard to diagnose via ultrasound, endometriomas can, but again, they are hard to see and ovaries sometimes hide too!

Thanks ausgirl. The cyst they found is on the left, but this time the pain is on her right. She has been in hospital for 2 days now while they are investigating. They ruled out endo last year and I was really surprised actually. I told her to keep pushing for answers.
Not sure if they are removing or draining or what at this stage :(

I have suffered with ovarian cysts for years. I do not have endo at all and am able to fall pg quite easily which is good.

I have had 3 hospitalisations for cysts all on my right ovary. It is actually 3x the size of my left due to scarring.
In all 3 of those experiences they have burst leaving excess fluid to float around causing extreme pain. As you said, vomiting, shaking, fevers and pain that not even morphene or any other pain relief could stop.

They were drained via keyhole surgery except for one as I was pregnant ( looked about 8 months pregnant due to swelling) and they thought it would be too risky.
So I just had to wait for the fluid to be absorbed.
Mine were from ovulating the doctors said but I still don't 100% understand it all.

I really cant quite understand why they wouldn't have noticed it on any scans! I feel really upset for your friend going through this!
They wouldn't have to remove the ovary but if she is in lots of pain I would imagine that the cyst has ruptured.

Deedles, sounds awful :( She has been on morphine for a few days now in the hospital. Should find out whats going on today hopefully, but it does sound very similar to what you have explained.