"After her solemn profession or perpetual donation, the nun can, if she wishes, receive the Consecration of Virgins. This is a special rite where the Bishop gives the nun not only the veil and ring, external signs of an indissoluble union with the divine Spouse, but also the stole. This confers on the recipient certain liturgical privileges the most significant of them being the proclaiming of the Gospel on certain occasions." (http://www.chartreux.org/en/nuns/index.php)

"It is a consecrated nun who sings the Epistle at the conventual Mass, though without wearing the manible. At Matins, if no priest be present, a nun assumes the stole and reads the Gospel." (http://www.newadvent.org/cathen/03388a.htm)

These nuns do not customarily vest as deacons and, while they do certain things usually reserved to deacons, they do not do anything that requires the power of orders. They do not sing or read the Gospel at Mass as a priest is present.