As far as breeding, really not sure on that... and it looks to me to be a tearing scar... you see them sometimes when a snake escapes an enclosure with a wire lid... they basically scrape their entire dorsal in so doing. But yet also looks like burns.
I know people that have bred scarred and *damaged* snakes to no ill effect. If you are seriously considering it, I would contact a vet that also breeds and get their opinion. They may have more concise information (emotive responses are good - but concrete answers are good too) regarding her physical capacity and potential damage, or just areas of concern.
As far as being a YB. I would never think that by looking at her. YBs have such specific belly patterns and even the manner of blushing does not look YB. I would say hands down no... just my two hands mind you.
Bruce