You know, my mother died about a month ago. Probably not the best example to use.For example, how can I say that an object such as a pen is still a pen if it has faded away from existence? The pen (or, in this case, a living human being such as your mother) is someone very special. But when it fades away from existence, you can no longer say that the pen is still a pen just as you can no longer say that your mother still exists. The human being (your mother) no longer exists. She is no longer a person anymore. So she is nobody now just as how the pen is no longer a pen when it fades away from existence such as being burned away by fire.
I'm just not seeing how someone's body dying necessarily leads to their non-existence.