The answer depends on whether or not you have a contract with that agent, and if so, what type of contract it is as well as its terms. If you have not signed a contractural agreement to list your property with her, then you have no responsibility to her.
If, hower, you signed an exclusive right to list contract with the agent, check the terms of the contract. How long does the contract run (all contracts in Pennsylvania require a start and ending date), how much notice are you required to provide if you want to terminate the contract, and in fact, is termination is allowed.
If you have signed something with the first agent, other than the Consumer Notice, I would urge you to contact an attorney to review the original listing contract and certainly make the second agent aware that there may be a conflict.