Why is my five year old cat so greedy?

am i giving her enough food?she has a full dish of cat crunchies,in the morning then i give a bowl of half tin wet food mixed with crunchies,at luch then rest of tin with crunchies at dinner time,this is quite expensive,with the tinned food everyday aswell as crunchies,but she always seems hungry and runnin round after about an hour,anyone been through anything sim?thanks for answers,shes a very spitefull cat too,and just seems to come in just for food and sleep then she pisses off she dont like hugs,