Um... yes, actually, reading facial expressions is a very basic human skill, and when you are making someone uncomfortable, and they are looking at you like “What on earth...” you should be able to recognize it.
This is ridiculous monkeys communicate non verbally. We are humans. We speak! So let me get this straight if the bitchy looking blonde with permanent dead pan face suddenly smiles at me then I am good to go? She might as have “come f me” message tattoo to her face?