'Ameena Ashcroft' (Grace's friend from Lincoln university), I feel is an overlooked victim in this case. Having known Grace very well back in the UK, she was also one of the last people to converse with Grace before she entered the hotel.
Her account of the conversation they had was that Ameena was alarmed by Grace's description of her date. Grace had described the suspect to her as an "oil manager" with no proper "fixed address".
No doubt she had worked out immediately, that a 26 yr/o in such a senior role, wouldn't in all likelihood be living in downtown Auckland, in transitory accommodation, dating backpackers for short term flings.
She was right to be unnerved, but she clearly did not want to spoil Grace's enjoyment of the date with talk of safety, suspicion and fears. Had she acted, she may well have been able to change Grace's course and save her life.
But she wasn't to know. I feel very sorry for her. I hope she does not blame herself for what happened. It is a difficult call in those circumstances when you have a gut feeling that something is wrong: but in the end what can you do?.