building a relationship takes time, however meeting an agent on the fly will in most cases deliver the result you had disappointment. As the previous agent stated you needed to have some conversation and expectations of how things would work prior to you visit. As well as when you arrived. the listing agent works for the seller if you don't need representation then you don't need a buyers agent to help you. Again the selling agents job is to protect her client. It would serve you better to hire a competent buyers agent.
Hello seller I would suggest you weigh this out heavely. Unles you had lots of showings on this house and multiple offers I would extend. Sometimes we gotta give a little more up front but in the end your life goes on. I would advise your selling agent to convey your frustration to the Byers agent and make it clear you are extended as a courtesy and want to move the process to close quickly. Yes you can DENY them it's your choice whether to extend or not but read your contract and most Of all decide if the sale is worth it.