Chicken walking like a penguin

I have a hen, her name is Elvis because she has a black comb that falls over. She’s 1-2 years old. A few days ago she started walking like a penguin and now she will waddle around and eat, but the other girls started attacking her so we brought her inside to see if improves, does anyone know what could be causing this? She seems fine with temperament, she’s clean, I just don’t know why she is waddling now.