Why does my cat follow me when I walk my dog, screaming at me and not letting me touch her?

Bean used to live outdoors until my my sister's friend found her under a deck. We took her in three years ago. She had seven kittens and we kept five. She is mean to her offspring but has been getting nicer to us slowly. When we walk the dog at night, she sometimes follows us around meowing at a distance; when she catches up and we go to pet her, she runs ahead, waits, and the cycle repeats. Why is she so concerned and not letting us touch her?