I have worked with a significant other in the past. My suggestion is to be open and honest. First tell her what you admire about her, ask her what she thinks is positive about the work you do, ask her where you can improve, and if she is sharing with you in a negative way...let her know how to make suggestions in a positive way.
Starting off with a positive, will allow her not to on the defensive. Another way is to pick one day out of the week that is a "work meeting" where you can discuss what went right and where both of you can improve. It might be a nice bonding experience.