Marion Cavanuagh and Bethany Young Connection

In the 5x07 promo, they show us three more drawings from Bethany. One shows a woman falling from a building. Sounds familiar? Marion Cavanaugh aka Toby's mom also fell from Radley. Spencer searched for answers about Marion back in Season 4 because she thought that Marion couldn't have jumped and it wasn't suicide. We find out in season 4 that a "fragile" patient had pushed her and the crime was covered up. Who might this fragile patient be? Is it Bethany herself or was it Mrs.D? Bethany definitely didn't like Mrs.D.