Unfortunately, Laureli is right on.  My wife was raised with three brothers.  She worked in a male environment.  She told me just what Laureli experienced.  I poo pooed it. So we decided to tested it.  

We went into an building supply separately and I listen in on the exchange.  After I witness the difference, I then walked up and identified with her and the sales clerk's voice tone change entirely.  Not only that, my wife asked the question and the clerk directed his answers to me.  

Both my daughters have repeatedly experienced the same thing.   

So, we still periodically will come in separately and I listen in then sidle up. It happens way too often.  

What is really funny is that it can be even worse when my wife or daughter knows more about the subject or the product than the clerk.

In the businesses that I worked with, I made it a point be mindful of this dynamic and not talk down to women.