It is not possible to remove a kidney during caesarean section as kidneys are retroperitoneal organs higher up in the abdomen and require a different plane of dissection. One in 5000 person is born with one kidney only and may never know about it unless an ultrasound or scan is done. Unfortunately in these days of misinformed but sensationalistic media coverage, routine regular procedures/surgeries have led a common man to suspect the intentions of every doctor. Your friend can have cystoscopy done to see if there are one/two ureteral openings. If there is only one kidney by birth then there is only one ureteral opening in the bladder. If a kidney was removed the bladder will show two openings. It may have to be done if your friend despite counselling is not able to remove this belief from her mind.