I've never seen an icon like this. She seems to be dressed as a bishop.
She is wearing a mantiya of a bishop or archimandrite. This image, called Gerontissa
) is a variant of the Abbess of Athos
, a reference to her being the patron and protector of the Holy Mountain, known to the Greeks as The Garden of the Mother of God (To perivoli tis Panaghias
While she is known as the Abbess of Athos, to show her in a mantle, and of the type worn by male clergy or archimandrites, is not correct. The Abbess title is figurative, not literal, so she should be shown in her conventional garb. Moreover, obscuring her clothing robs the image of much of the symbolism of her garments. Here is a more acceptable version, though it would have been even better if there was a motif of Christ present somewhere, either in the upper border, or in an upper corner: