Splints look good to me.
You mention medicated chicken feed. If you are in the US, medicated starter usually contain Amprol/Amprolium which is a Coccidiostat to help prevent Coccidiosis. It won't hurt her of course, but it's not an ingredient that would offer extra support to leg health nor...
The poor thing!
If she doesn't have the hobble on, do her legs just splay or turn out? She may have a leg bone disorder that can't be fixed.
You can try splinting the legs to see if that helps and place her in a sling for short periods of time during the day to help keep her upright and...
I would try vitamin therapy. Give her 1/4 tablet B-Complex daily.
PND does not contain B2(Riboflavin) and this is what you want...so there's a reason why I'm suggesting the B-Complex.
It's possible it could be Marek's disease even if she was vaccinated, but I would treat as injury and go...