I have several women on my team whose husbands watch our matches. I have never seen one of them give advice without it resulting in a sarcastic comment coming from their wife/girlfriend!!
That being said, women play so differently than men that what you may suggest may not work for her. Also, if she happens to get one of those "*****y" opponents, and you are giving signals, she can complain about coaching. I know you mean well but personally I would wait and see if your wife asks you for advice. Hope I haven't offended you