Satoko says that the shard doesn't even break her skin when it definitely feels sharp enough to do so. More than likely it's that Eua is stopping her from ending the game too early. Highly doubt the Witch of Theatergoing wants the show to end like that.
While that's true (and she can also use a knife), Satoko is the type that has most of her strength in the element of surprise. That's gone now, so getting up close and personal with a bat is very risky. She's also starting to panic.
We still gotta worry about the Looper sword. Also, when Satoko threw it into the lake, it had a piece missing from that panel. So we might still get a DBZ witch battle, just with everyone involved now.