I'm so sorry that happened to you and your friend!
Usually with harassment, I see experienced Moms here recommend starting with the company before going for a nurse-in. That allows the company to apologize and train its staff (which is really what we want!) without the embarrassment of a nurse-in. If they don't apologize, well, then it's time to stage a nurse-in!
Have you reported the manager to head office? If so, what did they say?
The law is on your side "Ohio Rev. Code Ann. § 3781.55 (2005) provides that a mother is entitled to breastfeed her baby in any location of a place of public accommodation wherein the mother is otherwise permitted. (SB 41)" (from http://www.ncsl.org/?tabid=14389)
Also, if she needs ideas for letters, or wants a letter proof-read before sending it, there are a lot of experienced moms here who I'm sure would want to help.