I just can't see anything in any of this that screams so angry, despondent, or whatever that Rebecca would commit suicide directly after a call from the hospital.
They only mention the last call. What about all her calls and texts and VM's made and received that day and evening. All should have been studied to evaluate state of mind, goings ons, general activity surrounding RN on her last day on earth. And as to that last VM: who's to say that it wasn't a message that.....someone was being sent over to collect something, and Rebecca should let them in. Voila, Entry. The hypothetical killer could then have had his will once in the house and suitably subduing RN, and probably also know he would need to erase that VM.