It is the open steps. As previously suggested, cover them with a runner. Then use high value treats and place the a treat on the lowest step. Repeat the process until she is very comfortable going close to the steps. Then place treat on next step until she is very comfortable with the second step. Hopefully she will place her paws on the lowest step to get to the treat. Then with the next step where she will definitely place her paws on a step to get the treat. Continue until a treat is in the camper. make this a fun and happy game with lots of praise.
My lab was that way. She was terrified of the open steps, but I made a runner of outdoor carpet from Lowe's and fastened with bungie cords. No more problem.