"Loose" spur is her right one?
Her left foot looks more swollen than the right to me. Is there a greenish tint to her skin on the foot?
Any signs of infection, bumblefoot or anything on the bottom of her feet?
When was her last egg? Any swelling, bloat or feeling of fluid in the abdomen?
Is she pooping, what's that like?
Crop emptying?
I'd work on hydration, if you have electrolytes, that would be good. Once drinking, then offer some feed (wet or dry), a little egg to entice her.
Have you ever had respiratory illness within your flock or other birds with symptoms of Marek's?
I agree, it seems more is going on than just a loose spur.