I don't claim to know what it's like to be a woman in a heavily male-dominated field (or just your de facto patriarchy, for that matter), but I also don't assume anyone I'm talking to at a conference has any reason to believe I possess any sort of prowess or authority without my convincing them of such even while donning my geekiest T-shirts.
More importantly, I assume anyone representing a product or service at a show is knowledgeable about its inner-workings until they give me some reason to believe otherwise regardless of their gender or attire.
While I appreciate that it is often difficult dealing with misogyny at conferences, I think it's unfair to lump a proper PR employee in with a model in a Princess Leia slave bikini who knows nothing about the product.