Kiwi asks…
Isn’t it more accurate to call it “glass shoes”, not "glass slippers"?
Answer from a Native speaker

Rebecca
Glass shoes could be said, however, the exact type of shoe she is wearing is called a slipper. When this story was written, the shoe she is wearing was called a slipper, unlike the house-shoes that are called slippers today.
Listening Quiz
1/2 STEP LEARN