Hillary suffers from a lower back injury. This can be deducted by her gait when walking as she throws her right leg outward ( rotating outward ) when taking a forward step.
She has Circumduction which is a common walking “problem” where someone will swing the leg out to the side to prevent the toe from catching on the ground. Several things can cause this such as foot drop, spasticity, a “stiff leg”, and/or weakness due to a brain injury, stroke, multiple sclerosis and a variety of other neurologic injuries.
You can see this in some vids of her walking.
She may have been suffering from lower back spasms locking her in that position. A common reaction is to place ones hands behind the spine to aid in support.