Sen to Chihiro no Kamikakushi, Mimi wo Sumaseba Recommendations
Both are Studio Ghibli films and both deal with the a girl's emotions in different ways.
They are oth coming of age tales with romance and basically little kids growing up. They have the same artwork and the same feel to them. If you like on you will like the other.
They kind of complement each other, since Whisper Of The Heart is realistic while Spirited Away is allegorical, but they have pretty similar discourses, both are coming of age tales, main character is a young girl, and plot deals about basic child/teen emotions like first love, responsibility and such... No wonder Miyazaki wrote the script for this one too.
The artwork is a little different, but still in the Ghibli standards.