When I first bought my Harley my wife had ZERO intentions of ever getting on a bike. I rode several times by myself, but the trips were usually short, as riding completely alone wasn't much fun. One very warm spring day my wife said if you are very careful I will take a short ride with you. I took her on some quiet country roads near our house and never went over 35 mph. She must have enjoyed the trip, as she asked to go again a couple of days later. I used the same approach as the first time except increased the speed to 45 mph. This lasted another 4 or 5 rides until I finally got her up to 65mph and she was calling me at work on hot days telling me to come staight home we were going for a ride and then stopping out to eat. Now it is never a problem getting her on the bike.
For a woman who likes clothes and shopping a trip to a well stocked Harley dealership sometimes helps to.
A little $ spent on something she feels comfortable wearing, without being all "biker attire" can make a big difference.
Just as we sometimes put on a "work" personality we can put on a "motorcyclist" personality. I say motorcyclist instead of "biker" because for someone who doesn't ride this seems to be more acceptable.
Hope you keep going on longer happy rides with your lady!