Because, other than sightseeing, she broke her thumb.
Or, rather, her "other" thumb, falling on the ice while commuting home from a party. Also messed up her shoulder. Her shoulder is likely the bigger problem, but that doesn't make for as good a "story".
"Her other thumb?"
Yep, in January she broke her left thumb. Apparently, her right thumb felt neglected, so she broke that one just before Christmas. Wasn't that nice of her to make sure she had matching thumbs. :-O