My wife and I were playing the other night and we had a magmar smokescreen
controversy. This is not a typical smokescreen question. We have searched
through all of the questions and have not seen it addressed. Here's what
happened. I had a magmar with one fire energy and used smokescreen. My wife
also had a magmar with one energy attached and she choose to smokescreen on
her turn. She flipped a coin and it came up tails. I attached another fire
energy and did a smog attack. She said wait a minute I used smokecreen and
you need to flip to see if smog worked. I told her that her smokescreen
failed when she flipped tails on her turn. I read the card and it says if
tails, that attack does nothing. I take that to mean that nothing means
nothing. Her smokescreen didn't happen and I don't need to flip a coin on my
attack. Is that correct? I would greatly appreciate an answer to this
question. Thanks.

You are correct.  When her tails came up tails, it means that all effects of her attack, including the smokescreen effect, did nothing.  So, you were free to Smog away.