You might could try getting her barn buddy out first. Then saddle and mount them both at the same time. Another trick I used was to load my horse into the trailer and take him/her somewhere else to ride. Usually on a trail ride with Frog and friends. Since we rode in so many different places, the horses never had an idea of just where home was. They are then dependent on you to get them back to the trailer and home. : )
But none of that is fixing the problem if it's that she won't go by herself.
Becky