Here is how it looked:
As I suspected, she went for the balloons first:
The Princess seemed a bit confused...
Then she realized that she was wearing a bathing suit and it was all over.
Dropped in a few Crayola bath tabs to color the water.
Cut out some foam paper in the shapes of apples and leaves and wrote A's on them with a marker.
Added a few dollar store apples and balloons.
Painted the tub with a shaving cream and food coloring mix.
To make it super special I burned apple scented candles. It smelled like a fall festival.
Afterthought: To put it over the top I could have played some apple-ishy ???? music and served apple cider.