It took some time for mine to feel 100% comfy on the back of our Ultra. The reason was that she didn't like having the TourPak behind her and the 2 speaker pods/armrests on the side with no way to escape/jump if something's wrong. Not that she would jump if we were moving but you know, it's completely psychological. Passenger handrails were out of question.
Now, she's completely fine. I'd say it took her 4 or 5 long rides.

Give her some time and ride easy for a few days until she's completely reassured.

 

When I put the tour pak on my standard my wife complained, I thought she would thrilled but she also said there was nothing to hold on to. Says she used to hang on to the sissy bar and now there is nothing to grab. So I put the hand rails on and she claims that did the trick. If you want her to ride just try to give her what she thinks she needs. Very smooth helps. Good luck with all the advice.