Wonderful black & white movie that I saw on television one summer probably mid-1960’s.  A child witnesses her mother’s murder, but she can’t tell who it is.  She is admitted to a mental hospital or sanitarium for play therapy to help reveal who the murderer is.  She keeps drawing pictures of Indians (Native Americans) wearing feather headresses.  Turns out that the murderer is the child’s aunt who was wearing a hat with feathers on it!  During the movie, the child also undergoes “water therapy” in an immersion tub & is nearly murdered herself by drowning.  This was a wonderful “Bette Davis-esque” movie that I loved but have never been able to find again!  Thanks for your help.