Does all of her poop look like the color of egg yolks (yellow)?
Has she been wormed?
Give her a bath in some warm soapy water and clean her up. Try to get all the poo form her bum and vent.
After cleaning her up give her a soaking in a warm epsom salts bath. Feel of her abdomen to see if it is swollen, hard, soft, normal, etc.
She could be having some type of internal laying/reproductive disorder. Something like Egg Yolk Peritonitis, Ascites, tumors or cancer can cause leg weakness.
She look like she may have some peck marks, possibly a bit of fowl pox and favus on her comb, but that wouldn't cause the leg weakness.
For the comb you can apply some iodine to the scabs to help them heal and dry up, don't pick the scabs off. For the white part on her comb (powdery looking at the back of the comb) apply a small amount of anti-fungal cream daily.
It's possible it could be worms, but generally it doesn't effect the legs like that.
If you have a vet that you can take a fecal sample to they can check for worms.
Peritonitis and internal egg laying issues:
http://www.chickenvet.co.uk/health-and-common-diseases/egg-laying-issues/index.aspx
http://scoopfromthecoop.nutrenaworld.com/tag/laying-issues/
http://www.hobbyfarms.com/livestock-and-pets/6-causes-of-chicken-swollen-abdomen.aspx
Worms:
http://www.the-chicken-chick.com/2015/11/control-treatment-of-worms-in-chickens.html