I would say it depends on how the cat is going to live. If Marley is going to be an inside/outside cat, she definitely needs some sort of identification. If you decide against the collar, the micro-chipping is a necessity if she's going to be going outside.

If she is only going to be an inside cat, I would microchip only and not worry about the collar. In this case, the micro-chipping would be in the event she escapes. I, personally, don't see the need for a collar on an inside only cat....if they're micro-chipped.