first of all, the scar will be on her left side, not under the belly (in front of the udder) if she has had a caesar. It will be about 20cm long and just in front of her hip, but down a little bit. Hang on, easiest way to explain it is to show you a pic.
This shows the location of the incision. This is about a week post kidding. Unfortunately its a little zoomed in but you can see her back leg on the right of the photo there, and sort of place the incision on the body. The pink stuff is to keep the flies off.
This is about 4 months post kidding. You can see almost all the hair has grown over the incision, you can see its the slightly darker bit because the hair is thinner and her skin is black; the scar can still be felt easily and if you know its there you can see it.
So that might help you a bit to decide whether it is a c-section scar or something else, and the age of it.
As far as whether she can give birth naturally, it depends on the reason she needed the c-section, which doesnt help you at all, I know. If it was a simple case of malpresentation (as in my doe's case) she should be able to deliver naturally with no problems the next time, provided they are not malpresented again. If it was a case of the kid not physically fitting out the pelvis, then the decision needs to be made whether it was an abnormally large kid causing the problem, or whether she is abnormally small in the pelvis. If the second case, she shouldnt be re-bred, unless she has widened out significantly with age. If the first case, she can be given another chance and if she habitually produces big kids that need c-sections, she shouldnt be re-bred.
Not knowing the history of your doe, its a little difficult. I'd assess her size and weight, and her pelvic capacity, and if I find those adequate I would breed her and see what happens, if she needs another c-section I would retire her. I always give my caesars a second chance but two strikes and they are out.