Commercial Broker unwilling to let competition Represent Seller

[Seth Estenson]

A friend of mine and I are looking at a commercial real estate property listed through Real Estate 7 brokerage in Devils Lake, ND. My mother in Law is a licensed real estate agent at a competing brokerage. I  initially stopped in at the business to introduce myself and tell them I was interested in the possibility of purchasing the business as long as I could have my mother in law represent me as the potential buyer. She (The owner) said she had no problem with that, but when I had my mother in law contact the agency(Real Estate 7)they said they would not allow it. What do I do from here?