Is it a sacrament? I think so.
Is it purely a non-liturgical ministry? Not in the byzantine tradition. The liturgical role is similar to a subdeacon; the extra-liturgical role is similar to that of the deacon.
It it a female Deacon? No. Nor is it a female subdeacon.
Is it a major order: by virtue of ordination by laying on of hands, yes. By virtue of institution within the 1st century, as with Deacons, presbyters and the epsicopacy? yes; Phoebe was a deaconess, and is mentioned in Paul’s writings. By virtue of institution by Christ? no, but then neither is the deaconate; both were established by the Apostles to fill specific needs in the community, and the role evolved from there.
In the west, it was almost purely an honorific; in the modern Eastern Orthodox east, it is a liturgical ministry in the churches that have used it (Greek and Russian), allowing a priest to have a deacon for liturgy in women’s monasteries, and for presanctified in the absence of priests. (The Russians seem to not be currently using them, and the greeks only recently started doing so.)
In the Oriental Orthodox, they are minor orders, ordained by acclimation and investure, not imposition of hands, and do not have any liturgical ministry (but are EMHC’s to women who are in need of viaticum), having instead public ministries, especially to women and children.
I would not object to Deaconesses as major orders, provided that it goes no further. They are not and can not be transitional; it is a ministry of its own.