Hi Capuccino,
I think u should make sure whether her chocolate cyst in overian or uterus, usually after operation,there is not really a problem for pregnancy. Also you should ask her how much the size of it. If it is small around 5cm,it should not be a problem assuming the skillful doctor did the operation(I trust private doctor more than the public hospital)
Repeat again:If chocolate cyst about 2cm or we may say 5 cm,the doctor usually ask u to wait and see whether it keeps growing,unfortunately,it grows,the only method is operation because this kind of cyst will not disappear by itself.
Whether it will happen again or not, it depends on hormone. Once you have imbalance hormone happen,anything can happen,breast cyst,overian cyst,uterus cyst and so on.
Method to avoid: Have a happy mood. Eat healthy, try not take spicy food, do exercise(because exercise can adjust our hormone in a good way)
Eat regularly.
How can u help her? I think you can go out for exercise with her after recovering. Find something to learn together. Go with her to see other doctors to get more advice. Tell her after recover and when she is ready, just try again. Don't let herself in a sad period for a long time. To be positive, u should tell her there are many ppl trying to have baby again and again due to miscarriage,health problems, operation, one tube cut and even they never know the reason.
I hope I can help.