[@ERode]
Doubt and uncertainty would probably be one answer. 

The other could be her selfish desire is to incredibly and undeniably powerful, but she also cares about the prosperity of humanity because immortality is boring alone. What use is being the greatest if there's no one to toast you or hold parties and events in your celebration?

She naturally wants to help people because it's the right thing to do, but it also help helps pad her fragile(?) ego.