Miko is acting aggressive towards her biological sister

A few weeks ago my kitty Yumi was diagnosed with Renal Kidney Disease, she stayed at an Emergency vet for about a week and was stable enough to come home. Yumi & Miko are biological sisters and have always gotten along. Why is it now that Miko only tolerates Yumi & one wrong move from Yumi and Miko growls and hisses. Does anyone know why Miko behaves like this? I rush to move Miko when this happens so that Miko does not hurt Yumi. Is this some sort of survival instinct, does Yumi smell that much more different to her sister now that she is sick?

Asked by Yumi on Nov 8th 2012 in Aggression