Lactivism has been a necessary political development based on the ongoing discrimination mothers who breastfeed experience in many aspects of their lives. Given the outrageous and discriminatory stance, that your own employees don't even approve of, leading to overcharging for breastfed babies in your care, it was only a matter of time before you were targeted for activism.
Your stated reasons about the "biohazardous" nature of milk and the "added expense of handling it" don't hold water. I have looked at Ohio's regulations regarding the handling of formula and of breastmilk. If the rationale is to charge for that which requires more special care and work - formula requirements are clearly more onerous!
The national lactivist movement, which I am extremely involved in, has been very successful at drawing media attention to businesses who discriminate--think Starbucks, Delta/Freedom, Borders, Toys R US, Victoria's Secret. All took a PR
hit and were forced to apologize and change their policies. Do you really want your daycare center to the be one cited in news stories for the next year or so while an Ohio contingent of lactivists conducts protests at your business and gets a law on the books that prevents daycare centers from discriminating against breastfed babies? Do you really think that your business will thrive with that reputation - given how any smart 2007 mama will google the name of her daycare center to see if any bad things have happened there?
I am sorry you have such a negative feeling about breastmilk, the optimal and safest form of infant nutrition. Often times mothers who were unsuccessful with nursing or felt judged for not doing so have this attitude, but you are a business woman and you need to think beyond your own personal bias. From a health perspective you are in the wrong, from a business stance you are in the wrong, and- in my opinion- from a moral stance you are wrong. Please consider your next steps carefully. A press release announcing a change in policy and a refund to the mother in question of all overcharges would be a great first step.