She may not have still been hungry or even mistook you for a mouse, she may have just still been in the hyped manner of all hunting snakes. Some will stay hyper alert to heat or movement near them for awhile after they are done eating, some will go off immediately to their hides. We are fostering a young boa here that is sooooo hyper when she feeds that we use an old dark blue pillowcase to drape over her enclosure for feeding time and awhile afterwards. If not she'd knock her self silly against the side of her tub, striking at anything that comes near her home.

Watch the baby to make sure it does get that jaw back in it's proper place. If it hasn't by morning then you might want to at least call the vet and have a chat. Usually they will yawn repeatedly and pop everything back where it should be.