Ivy is quickly getting good at the whole sitting thing. She can often balance for minutes at a time now! There are still frequent face-plants, toppling and folding in half, though. If she leans too far back there is nothing she can do, but she can often rebalance herself from falling to the side or forward.
About a month ago
My hands, just out of shot, ready to catch Ivy when she topples:
And now she can balance well enough that I can even leave the room (very quickly) to grab my camera. She was staring at Charlie-dog for a long time, leaning towards him. She wants to be on the move already!