questionable tactics

I was threatened that if I did not sign the Offer to Purchase from the buyer within 48 hours that the selling price would be reduced by $25,000. This was set up by her realtor who then wanted me to sign a contract with him as part of the deal. He had the buyer before he found a seller. In effect, he was selling the buyer to the seller, me, forcing me to pay the full 7/3 commission. Very fishy!