I forgot to mention that as of last Thursday, Peach can sit up on her own now! She cannot get into sitting position by herself, but she can stay there if you set her like that.
Though she doesn't usually like to stay that way because she can't move around. On her belly she can pivot a full 360 degrees using her arms, or she can roll around to get to something she wants. She also can't get out of sitting very gracefully yet. Often once she's done she'll just throw her head back or flop to the side.
I think she noticed the coffee table needed some fixing. Oh wait. Maybe her tooth did?