Egg binding usually has a strange upright walk - kind of like a penguin or the stance they take during the final push out of the egg. You could probably gently feel around the area of the vent for an egg or carefully use a lubed glove & finger. Her comb color looks like she's healthy & laying, so it could be that. I've never done the glove test, but if I suspect a hen is egg bound, I just give her a little spa time in a warm tub followed by some rest in a quiet darkened area. They really like soaking, it relaxes them, and why not have a clean hen. I also feed a little extra crushed eggshell to increase calcium.
Check her crop and feel her bones. Chickens hide injuries & illnesses well. Perhaps the roo was too rough and pulled a muscle. Hard to tell.
I hope others have some ideas.