Her problem with your other dogs I can help with .
If you realy want to sell her I promise you asking money makes her a lot more likely to be bred from if she fails to work cause someone will want their money back . Get her spayed and ask spaying price only and she will soon find a home .
Are you selling her with papers ? if u r and you dont want peps to bred then u should have come up with a reason for this even a load of rubbish but bottom line is she is too old if she is a pet to now go on to racing kennels with zero history just for her breeding as they need to worry about lots like r