I keep jumping up and down on this comic, because the scales on the top of her face look like shadowing if its not a close-up or hightlight shot of her.
On another note, this maid has horrible luck it seems.
Considering she remembered the boy grown up in her first strip, is this just a matter of her not actually understanding language instead?
It seems so. The boy never actually 'spoke' to her, they only communicate with gestures. that comic also has no dialogue bubbles, implying that this mermaid doesn't understand human speech.
The half-dragon girl trying to explain maid and cafe only made it worse.