I love XKCD! And today's comic strikes that perfect balance between sentimentality and philosophy.
Clearly father is a spatio-temporal continuity theorist of identity. If the aggregate breaks up, then its GONE. But daughter is something like a mereological theorist of identity, if you're made up of the same parts, you're the same, or in this case.
I have to give it to father here, since daughter's notion is almost incoherent. If she is an organ donor, and she continues to exist after her death, then she could exist in multiple places after she is dead, since she has multiple organs that could be donated. Even worse, her organs are made up of things like tofu chicken nuggets and vegetarian tikka masala (I imagine she's a vegetarian). So SHE really is just donating some soy protein to others.
If she would exist after death, then the same can be applied to what makes up her organs. She could continue to exist just as easily as checking the cannibalize box on her driver's license.
What your state doesn't have a cannibalize box?