There is no evidence that she was killed. There was however a "pot of boiling water" on the stove. An inference can be made about how much water was left in the pot when it was found that would be a good indicator of jow long she had been missing. It is very unusual that someone was "sent" to check in her after she didn't answer calls but found a pot of boiling water. Even 2 gallons of water would boil dry after 7 hours maximum, even at 75% relative humidity. A reading of the power meter would also have been a good indicator of how long it had been since she set the water to boil as a spike in energy usage from a 240v oven outlet. It is very reasonable to assume that the police have not released all of the evidence in this case and I would say they have in fact released almost none.