When you say "she" has a buyer's agent, I think you are referring to your mom. If she signed an agreement with someone to be her "buyer's agent", that agreement indicates that the buyer's agent company will be paid a certain amount of money (decided on at the time of signing) on a completed transaction. Finding the home, is just a very small part of the whole house buying transaction. That is when the work really begins and your agent is going to be helping find comparables so that you know what price you should offer, negotiate with the seller to get you the best price, arrange for inspections, closing agent, and pretty much document this whole transaction from beginning to end. I would not want to navigate a home purchase these days without an experienced agent given all the laws and regulations that are in place, such as due diligence, etc. But to answer your question about obligation, if the buyer signed an agreement with an agent for their services, there is an obligation, no matter who finds the home. I hope this answers your question.