Iodine is not going to do anything for her scar and I wouldn’t use it; not because it’s dangerous (because it is not), but because it won’t work. If her scar is well healed and not noticeable, she might try mildly stretch it lengthwise and width-wise and massaging it daily (not long) to try to make it more supple. Surgical scars can be tender for a long time.
If her scar is bumpy and darker than the surrounding skin and mucosa (the lining of the vagina), it might be a keloid formation around the scar which is just a reaction that some people get after a surgical cut. They are more problematic in that they don’t tend to go away on their own and stretch or massage won’t work.
These are just friendly suggestions. I am not a GYN and never wanted to be (if you saw what I’ve seen, you wouldn’t want to either). Just remember this. No one on this site, whether they are a doctor or not, is a substitute for a real doctor who can look at a problem and wave their hands over it and make it better. If your wife is concerned, have her call the doctor who did the procedure and get him or her to look at it and help her.
Good luck.