Those types of reactions just happen to some dogs. At least the steroids and Benadryl brought her out of it.
Vaccines do tend to make them sleepy for a day or two, but she is more likely to react because of the MVD. Since a reaction has occurred, always premed with Benadryl and the rabies should be given on a different day than all other vaccines. Some vets will write a medical waiver saying that a particular dog can't have the rabies vaccine and then some won't write one for something like MVD.
Watch her gum color and make sure they are nice and pink.