We have had a pair breed, then the next time we introduced them they started fighting and they are sexed 100% correct, it was a Spinner Male to a Lesser female. Theres no way to tell if she is gravid just by that because the time it happened to us the female wasn't even gravid. Have you tried palpating?
Oh and by the way we paired up the same snakes a different time after and they were fine. Have you paired them since?