Have you ever paid attention to the times she's pooping? You need to take her out close to those times. My three are very regular....everyone poops first thing in the am, Reggie will usually need to go again after eating breakfast, Rams goes around 2. She and Reese will go around 5 when we get home.
I'd say if you haven't pay attention to her schedule...you should.
Also make sure she walks during those times...walking stimulates their bowels.