I find comments like these endlessly fascinating due to how I designed these characters. For regular human characters (and Nell, for the most part), I gave them human proportions and facial structures. But for the pure fey, I applied a tiny bit of anime aesthetics. The Fairy Queen is the most extreme example of this.
Most likely, what is triggering the feeling of "cuteness" in the Fairy Queen is that she has slightly larger, rounder eyes than a real human would have. Her chin is more pointed. Her waist is unreasonably slim, while her breasts are too large for her body size. Her eyes are also slightly angled. Obviously, her ears are pointed, but I don't think we see that very clearly due to her hair.
These are features I gave her because there is something instinctive in people that makes them (especially the eyes) attractive. The jury is out on why that is, but it is a real thing.
When people first saw the Fairy Queen several years ago, people reacted very positively to her appearance. I found that a little amusing and highly fascinating because of how I had deliberately tried to make people react that way despite making her look inhuman.
