Just a thought...would she roost better if the roost bar was flat? I'm building a new coop and this time I'm using 2X4s wide side up as roosts so that they can cover their feet rather than curl their toes around a thinner roost. Maybe replace the roost she prefers to see if she keeps her balance. Heck, I might consider a 2X6 even. Just a thought but it couldn't hurt to try it.