At first look we can say the style of Anne Anderson's painting didn't change much in decades. But this would be wrong.
She loved bright livid colors through all of her life and she adored contrasts. It is easy to notice curves of just about everything, including the lines of objects which should be straight.
But we can also notice the contrasts in later years of her career were not so strong and even color red, one of her favorites at the beginning of her career, wasn't so aggressive anymore.
The illustration on the left is from one of best parodies of the romantic novels ever. It is titled Aucassin and Nicolette and it was probably written in 12th century. The illustration on the right shows similar fluid scene with lady on the run: Cinderella, which is even older.
In both cases faces are drawn with only very limited number of strokes with a brush but we can say the faces on the right are even more expressive despite the fact they are drawn with less moves. Anne Anderson obviously mastered her painting technique and she also moved from more realistic three dimensional paintings to two dimensional which are more favored by children (another famous illustrator Walter Crane wrote several essays on this subject).