No, your dog is NOT mental.

She just has a fear issue(s). My guess is maybe things that rolled used to be thrown at her, or something along those lines.

This is not something that will majorly affect her, unless she sees these round objects.

Honestly, when something Molly is afraid of, I watch and laugh. She tries to confront it, but never does and just jumps in circles around it barking and growling.

Maybe someone else will be able to give you advice on how to help her overcome her fear.