As the doc says: Yes, there's a hematoma (a nice buildup of fluid over the base of the thumb), but *why*? It may be "just" a hematoma (probably caused by a tendon snapping over a blood vessel and making it leak), or it may be one caused by a muscle tear.

And there's no way to know from outside. :) So we wait. She's leaning toward the torn muscle because of some of the other symptoms, but....