Lacking support of your boss
Analyze why your boss isn’t supporting you. Assume there might be a hidden deal he has made in connection with the current arrangement. The deal may have nothing to do with the business but with some of her outside (personal) interest. Stand up for more of her backup only if you can guess at least the background. Do some desktop search and/or collect some informal insight. Be extra cautious doing so, for colleagues would be more than happy to give feedback on your inquisitiveness to your boss.