Try not to get distracted by her presence. She's going to be chuffed just being in the cockpit - so don't think you have to give her a running commentary on what your doing.
Pick a route your familiar with - you want as little stress from the navigation so you can keep an eye on the guages and concentrate on your flying. Then worry about your other half.
Keep it nice and simple - no showing off - you're a pilot now - moving the thing is showing off enough in a non-aviators book!
In your pre-flight briefing, dont forget to warn her about turbulence and vibrations - in my case I forget to mention the stick on an R22 can rattle your fillings lose - she was only used to nice big jumbo's and when she saw the stick visibly rattling... she was a bit concerned!
Also tell her that there are times when you won't be able to speak to her - but as above, don't feel you need to give her a running commentary. If she's interested tell her things, but not to the exclusion of flying the aircraft.
Aviate, Navigate, Communicate (which includes pax!)
and enjoy!