re: Selling my house. Why do I have to pay the buyer's agent?

I just had a situation arise with a realtor for a house I have listed on Zillow that should add to the conversation. She asked for pics of my backyard and parking area. After sending, here is the email exchange.

Realtor:
"Thanks so much for this! I will pass on to my buyers. I guess my next question is, are you will to pay a buyers' agent commission of 3% if my clients decide to make an offer on this property?"

My response:
"If your buyers make a legitimate offer and we're able to negotiate a price that's acceptable I would definitely consider a commission. However, before putting the cart before the horse, I don't want to commit to a certain percentage until a legitimate offer has been made."

Agent follow up:
"Unfortunately, I cannot risk not being compensated."

How is this servicing your client and why should I pay over $20k for providing me with basically nothing especially considering her clients likely found the house.