We are definately looking into trying something like Feliway, and I will look for those drops the next time we go to Petsmart.

Just to clear up any mis-communicaton, Harley is not a kitten. She is a little over 2 years old.
Any time Sheba even sees Harley, she throws a fit. We have vocaly reprimanded, sprayed water bottles, and tried some mild counter conditioning.
I guess our next try is chemical but we are not big fans of it.