First off, you need to find out if her misunderstanding was warranted, either by her mistake or your companies. If it was your bad advertising that gave her this wrong idea, you should consider giving her the two anyways if your profit margin allows this. This could create a strong relationship with that customer. However, if she was just blatantly wrong and possibly trying to pull a fast one on you, tell her you can't help, and move the situation on to a superior if she decided to escalate it further.
