Hello Taylor K.! I myself have never experienced this but I would suggest starting with small baby steps. She may feel more safe as you spend time with her, playing with her to distract her from her absent mom. Maybe you could slowly reward her with treats the way out the door and along the walk to keep her unfocused on the walk. Also if she see's that her brother is about to go for a walk and having a good time it might make her want to follow in suit! But you shouldn't have to force her outside to face her fears. I hope this is helpful, goodluck. =:--)