Has any bruising emerged? I would suspect she damaged a tendon or muscle. Have you tried Epsom soaks? I would expect that could improve her function after a few days of twice a day soaks. B-complex also should be tried for a few weeks.
Arthritis, maybe. But I'm still leaning towards a minor injury. Study the running video. She displays full normal motion from hip to shank, then she pulls back before her foot makes contact with the ground. I bet she stubbed a toe getting up onto her perch. Yes, you read that right. I've seen...
Foot pain issue. Leg seems to move well, but the foot seems tender.
Foot injuries are not always easy to determine since the smallest thing can cause pain. I've found the following on limping chickens:
-pine cone scale lodged under a toenail
-hang nail
-broken nail
-bruised toe (light green)...