Instructions
Choose a Sim you don't much care about and instruct them to eat all the food in their food box by directing them to their food box and pressing the "A" button on the Wiimote, until all the food has been consumed.
Do not feed the Sim slated for death and wait patiently until he or she starves.
Direct another Sim to the place where the Sim died. Walk towards the grave and press "A" on the Wii mote to mourn his or her death; a death daisy will grow once your Sim has finished mourning.
Press "A" on the Wiimote again to collect the death daisy.