You might have to tell the customer to hold on a minute. And tune her out. Say mam a few times to her, so that it doesn't sound rude. But don't let people get to you. They are just stupid sometimes. That's there own fault. And occasional stupidity is part of the human condition, lol. She may have been worried that the manager would give a response she did not like. Cut yourself some slack. It's okay to have a stutter moment. Just continue to do the task the best you can. You did get the task done, that is the important part. And if the customer is just to crazy, get help: You can double team her, lol.