Choose your battles, and help your husband choose his.

If she has a request that will inconvenience you, but not put you out, discuss the issues with her, and grant her request. As long she isn’t repeatedly upsetting your routines, save your battles for a request that will cause more damage than a minor inconvenience.  When you do this, it keeps the battles to a minimum and gives the battles you choose more justification because you don’t always say no, only when you have to. This will also work out to your advantage because the more you help her out the more apt she will be to grant any of your requests.