Murder. She holds the gun in her right hand, but the pen, cigarettes, and soda can(?) are all on the LEFT side of her paper. It'd be a little awkward to shoot with your non-dominant hand...
I think what happened was she was sitting on the bench looking out the window, and the murderer shot her from her left side. She didn't see it coming, so there was little damage to her surroundings. The murderer then had to frame the scene to make it look like a suicide. He put the gun in her right hand because the gunshot wound was on her right side. But she was left handed!!! That's where he went wrong. Then the murderer wrote the suicide note. Just the fact that the pen is on the opposite side to what is expected proves there was someone else there.