Actually, there is an in-universe explanation of this.
A Friend's body is composed of Kemoplasm, which forms and shapes the Friend based on her perception of her original animal body. Kemoplasm varies in concentration depending on the area of body; the "base" human body is particularly weak in Kemoplasm compared to her clothing and, the important part here, her hair.
In short, those aren't actually ears, they just look like ears because the animal part of her still perceives her ears being there.

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