When I said treat it as you would a human death I meant in terms of sensitivity and response.
How we support people in bereavement or imminent bereavement can only have a limited and often unpredictable effect but by quietly taking whatever happens with the same degree of sensitivity is the best you can do.
When my father was dying I was pretty much forced to stay at university and I was given a rather mixed level of support.
Some of my student house mates kicked up a stink when I wanted to get a telephone connection to the house so that he and other family members could keep in contact with me.
This was even when I was prepared to pay for the thing myself and have it in my room because they thought I was emotionally blackmailing them into paying for it (If I had to pay for a connection it would make them look bad was their reasoning).
Now my father was much more important to me than my cat but I got more support for the death of a pet than I did for the death of my parent.
If I had the same amount of support the more impacting bereavement would have been more tolerable than it was and not less because later on a dead cat generated a similar amount of support.
Support is support.
I wouldn't suggest getting a replacement pet but keep your ears open to any signs of your friend thinking about it and then speak as you feel is appropriate.