|Perhaps the ranchers in the old Wild West were correct when they claimed that good fences make good neighbors. This notion has disappeared in today's open office configurations, and so has the privacy that used to accompany it.|
Your office neighbor may malign your customer relations skills, but the same could be done with her human relations skills. Listening in on someone else's business and then dropping a barrage of criticism is not exactly the way to build a productive working relationship.
Since she is no longer talking to you, that does not automatically mean you are not talking to her. You can try to reopen the lines of communication by approaching her and stating that you appreciate her desire to help you, but her feedback caught you off guard. Tell her that you would like to discuss her comments, since both of you could profit by reviewing various sales techniques and styles.
If she continues the silent treatment, you should mention the situation to management. Your associate may choose to ignore you, but a breakdown in teamwork is something that management typically will not choose to ignore.