Well, my wife started backpacking with me, so my perspective is a little different than trying to convince her to get into it, but here are some things I can think of that are different for her than if I go without her.
*Women's toiletries! Even if it's not needed at home right now, sometimes all the walking can create a need for them.
*More toilet paper. Remember they need it everytime they make a stop. Not just once a day or every other day that you might need it.
*Baby wipes to take a hobo shower. I know my wife likes to at least get a wipe down in the morning, especially her face. Dual use, if you have happen to need them...
*Let her bring a book if she likes to read.
*Stop and take pictures. Gives her something to look at at home and forget any bad memories and only remember the beautiful scenery and happy times with you.
*Treat it like a Union job; morning break/snack - Lunch break - afternoon break/snack
*Coffee or hot chocolate to go with breakfast. A warm drink in the morning does wonders for their mood.
*Let her have enough weight to make her feel like she wasn't a burden, but you carry all the community stuff like bear can, tent. Let her carry lighter community stuff like the stove, her own cloths, sleeping bag, snack, etc.
*Travel pack of tissue! For whatever reason, no matter how hot and dry, our noses run whenever we are hiking.
*Ear plugs. Helps her sleep if unfamiliar noises wake her up. Even if she isn't afraid of the noises, sometimes just the unfamiliarity will wake you up. It does for us anyway.
*Fully enclosed shelter(tent). Offers privacy, and a false sense of security. They like that. Remember, for the most part they tend to be more emotional than logical.
*Keep the mileage low so you have at least an hour or two before you go to bed to relax and enjoy where you are at.
*Try to do some day hikes in the weeks/weekends prior to get a feel for the mph you are able to do as a couple.