Chicken can't walk suddenly! SOS

[Rori]

I just moved my hens from a friends house to my backyard yesterday. A few hours later, one of my hens is struggling to stand and balance. It was a high of 105* F, so even though their new coop/ run is totally shaded it was insanely hot. With the assumption of it being heat exhaustion, I brought her inside and hand her lay on a large ice pack. She stopped panting, but as of this morning, she is still struggling to stand. She is a Rhode Island red, and a little over a year old. She is low girl on the pecking order, and is getting way more beat up than usual. she's got fresh scratches on her comb and face, which is pale and splotchy. She is alert, eating and drinking, and her poop looks great. The flock did have some exposure to the bedding from a sick piglet ( parasites?), but I have no clue if that short exposure could have made her unwell. Their current housing is a 4x4 coop with deep shavings and 3 nesting boxes, their run is 5x 10, with deep, coarse sand, with a larger yard to explore under supervision. Any thoughts or advice? All the other girls are completely unfazed.

 

[Rori]

UPDATE: Thoughts she may be egg bound, but she laid an egg easily while sitting on my desk. Pain seems to be radiating from the bottoms of her feet, where it looks like the start of bumble foot. I have soaked her feet in a warm Epsom salt bath, then removed the plug forming on each foot, followed by a saline rinse and Neosporin. Once her feet were treated and bandaged, she's moving significantly better, though you can tell that she is still tender.