why she has no wings?

Canonically Aya doesn't have wings, so its obvious some artists will depict her that way.

. . . so then why does she sometimes get wings then? @.o''
<-- *confused*

The wings are canon (Bohemian Archive in Japanese Red), only that she shows them when she wants.

FeKa said:
The wings are canon (Bohemian Archive in Japanese Red), only that she shows them when she wants.

I see, didn't read that one.