It's not so much that she is afraid of outside, she is just not used to the big wide world. Her security is you, and the closeness of the walled-in indoor areas.
Give her time and be patient with her. Carry on matter-of fact to reflect to her the positive example that there is nothing to be worried about.
Sounds like she was not socialized at all during before you got her, so EVERYTHING is new and overwhelming. Since she is so unsure about everything, take is slow to introduce new people or new dogs.