Any way you slice the commission pie, your agent is due a piece since she brought in the eventual buyer. But it sounds as though she may not have thoroughly represented you in the deal, though that can be a relative call given the two-sides-to-every-story axiom. Some may argue that since the buyer was introduced to the property through the efforts of the listing broker, then the listing broker is entitled to full commission. Others would say she did no follow-up work and hence, shirked her duties, leaving her client to directly negotiate and work out the particulars -- essentially doing her job.
First, you should know that agents can do a lot of legwork and incur major marketing expenses before showing a home, which can include sales literature, video tours and listing costs. These costs may have to be rolled into her commission regardless. However, there is no excuse for an agent not following up with interested parties after a showing. It's pure negligence or laziness.
I'm curious if you earnestly tried to contact your agent about all this as it was happening and if she didn't respond, and whether the buyer tried to contact her and she was equally mute. If both are true, you have a stronger case for a reduced commission. Also, based on what you say about your negotiations, your buyer did not have agent representation, hence your own agent may not have to split her typical 5 percent or 6 percent commission after the deal closes anyway. You can try offering her a flat 3 percent, which may be enough given the circumstances. She, on the other hand, may have a totally different idea.
Ideally, your listing contract should lay out all the duties expected of each of you. But there are always those little gray areas that remain open for interpretation. If she won't budge, you could say you will complain to her parent firm or the local Realtor's board. But if you try to sue, it will likely not be worth the expense and effort, given the undeniable fact that she brought you the buyer, satisfying your goal of finding a buyer. You may have to buck up and try to negotiate adjusted terms with the agent. It's like the old saying goes, "You don't get what's fair; you get what you negotiate."
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