She's probably having too much difficulty to get up on a roost, so she's staying on the ground. If the vitamins help then when she's moving better and more balanced she may start going to roost, or you can start putting her up there until she goes on her own. For now, make sure she's safe from predators at night, you can lay a short length of 2x4 on the floor of the coop for her, she may be willing to roost on that since it's not high. Or alternately you can crate her in the coop overnight if there is room.But she also hasn’t been putting herself to bed and I find her on the coop ground at night when I lock everyone up.