Sydney - Shelby

I have two Westies, Sydney and Shelby, both girls and sisters and 18 months old. I’ve noticed when Shelby walks her back legs go in circles and when she runs they flap outwards. She’s not very good at jumping, I have to lift her up if she wants to get on the settee or chair. She’s smaller than her sister, Sydney and very loving where Sydney is more independent, her ears have never stood up either, is her back legs problem due to her breed or is she just unfortunate to have this problem.