See my first advice would be see a good vet and have a thorough vet check completed on your girl. Dogs dont just fight over nothing. It is quite likely she is in some pain, think how grumpy you are and how much more likely you are to snap if you are in pain. Much more likely.
My first stop would be a very good chiro vet we have here in South East Queensland to have a thorough muscular skeletal and normal vet check done. If something was found work with the vet on fixing the issue (if possible), if something that is not fixable or life threatening (cancer etc) then I would probably start considering PTS, I would also consider PTS if health check shows up no signs of health issues, because then it may be neurological OR she may have just decided she no longer likes him, it happens.