I'm so glad you are going to do something!
There are less-experienced moms out there who would not stand up for their rights (and might not even know they have any). So, I think any time this happens to us, it is our absolute duty to try and fix the situation so it won't happen again.
Great ideas so far!! You could also...
~ print out a copy of your state's BFing laws and mail everyone who works there a copy, and post one of their bulliten board.
~ organize a nurse-in.
~ I would seriously look into who all her superiors are, and write them all a letter, right up to corporate headquarters asking for an apology. Explain the state law that she broke and how she violated your and your babies rights. Her actions were rude, improper, unnecesary and illegal.
The letter to the local paper is a great idea! I would mention the state laws, and the irony of a supposed health club shunning the healthiest choice for moms, babies, and society, and our enviroment!
People can be so stupid. If they were really interested in health, they would have commeneded you and would hassle the formula feeders.