Per other news sites, it seems she was dismissed from the hospital.
See #59, she may have been dismissed from that hospital building and been driven to another building.
WSJ
Hillary Clinton Makes Brief Appearance Outside Hospital
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WASHINGTON WIRE HOME PAGE
Secretary of State Hillary Clinton briefly left the New York City hospital building where she has been since Sunday, igniting speculation that she had been discharged and was going home. But she remains hospitalized after evidently making a short trip to another building in the large hospital complex.
Photos and video showed Mrs. Clinton walking to a car, wearing sunglasses and a coat, with husband Bill and daughter Chelsea at her side. She apparently returned to the original building later.
She was taken to New York-Presbyterian Hospital/Columbia on Sunday for treatment of a blood clot in her head. The blood clot, found during an MRI that same day, was the latest health setback in the past month for Mrs. Clinton, who became ill with a stomach virus during an overseas trip, then fainted and fell, suffering a concussion.