It seems weird that there was no sign of a struggle in the crime scene.
THe newspaper article says that the thing that made them change the case to Homicide was a small bruise near the left eye. They say that she may have been struck with a fist. It seems weird that there are no other signs of a fight in her body. Was she left unconscious by this fist blow?
Are there any case files still left from this? Medical examiner report on the location of the bruise specifically? If the bruise was on the front of the face near the left eye, it might indicate the position of a hand or fist in an attempt to forcibly drown her without clothing. Grabbing clothing to drown a person I would be easier that if the person is without clothing and nothing to grab and hold on to.