I'm lucky enough that I am able to take my boys on the morning of a weekday. There's rarely anyone there. I think you should keep trying a little bit more. I think Lucy will become comfortable with time.
Our big dog area is attached by chain link fence to the little dog area. Both my boys walk right up to the fence and try to great the giants. One time a huge German Shepherd barked at my boys and they zoomed away at the speed of light. Max has races with the big dogs along the fence. Oh, and I've taken Max on 3 separate occasions. He's getting a little less nervous each time, however he still plays fainting goat when a dog is chasing him.
If you go during a quieter time, Lucy can get comfortable in the area exploring on her own.