Also G has been commenting on others and even herself dying. I'm a firm believer in telling kids the truth but at their level and I've gone down the life cycle route and explained that everything that is alive, will at some point die.
That it includes everthing alive from flowers, plants, flies and spiders to cats, dogs and people.... that they all live for different lengths of time and that cats and dogs and people usually live for longer than flowers, flies and spiders for example. That things die for different reasons. A flower will last for it's lifetime unless you stand on it or don't water it etc. A fly will last for it's lifetime unless you squash it or it gets eaten by a spider etc. People usually live for a long time until they are old unless they get sick or have an accident.
For me it's about putting it into perspective and reassuring them that it's not something to be scared of. We haven't had this conversation all in one go by the way, she's asked bits and pieces over the weeks but I'm following the same types of answers.
Today it was about her pet fish "will he die one day?" My answer was "Yes sweetheart, he will one day but hopefully not for a long time, unless we forget to feed him or to change his water and look after him. He'll probably die before Mia (the cat) does though because fish don't live for as long as cats".
Every child, parent and situation is different though so I guess you can only really go with what you feel comfortable with... x