Macrina the Younger (ca. 330–379) came from one of those families where not only was nearly every Tom, Dick, and Harriet a saint or a bishop or both, but two were among the giants of fourth century theology (and it was harder to be at the top of the theological heap in those days than in some later periods). Her brothers Basil the Great (Jan 1) and Gregory of Nyssa (Jan 10) were two of the three great Cappadocian Fathers (along with Gregory Nazianzen (Jan 25), who only grew up in some other family because he chose the wrong parents) (no, I don’t believe in reincarnation) (sheesh). She was taught to read and write by her mother, (St.) Emila, but using only the Scriptures and holy writings, rather than Plato or (shudder) Euclid or any of those pikers. Gregory, in his Life of his sister, avers that this was per Macrina’s request. Thus she grew up both very pious and very smart, which is a darned good combination if you can pull it off.
When she reached betrothing age, her parents betrothed her to a pious young lawyer (don’t laugh! it’s possible!), but he died before the nuptials. After that point she refused all other suitors, desiring the life of a holy virgin, and wishing to remain faithful to the memory of her fiancé. And that, as they say in Greek, was that. She buckled down to pitching in, and was a great help to her entire family, in particular her younger brothers. She taught Gregory everything she (and to hear him tell it, everything he) knew, and when Basil came home from seminary all puffed up (we’re talking hubris not histamine), she taught him humility, as only a big sister can.
After her father died, she and her mother, with the help of younger brother (St.) Peter of Sebaste, retired to a monasticly existence, attracting (as ever happens in this sort of circumstance) a circle of disciples (or a square, or a trapezoid—does the shape really matter?) including some of their freed former slaves. Macrina wrote a monastic rule for the community, which her brother Basil used as a model for the monastic rule he created, which became nearly as important in the East as Benedict’s was in the West (indeed Benedict (Mar 14) had Basil’s rule at his elbow when he crafted his). When Emila, who had served as the first abbess of the institution, died, Macrina took her place. She was devoted to a strict asceticism, sleeping on a board even. For this and other reasons she was granted the gift of wonderworking, which she used in times of famine to keep the monastery supplied with bread. The nuns also told her brother Gregory (while he was doing research for her Vita, we suppose) that she once healed a young girl of an eye affliction. If they told Gregory what that affliction was, it didn’t make it into any of my sources. But it was afflicting, you can be sure.
Shortly before she died, Gregory made it to her bedside, and they had a wonderful and loving conversation that he used as the basis of his theological treatise Dialogue on the Soul and Resurrection, which was actually called Ta Makrinia, which Google Translate parses as “distal” (I’ll let you look that up). One source gives her last words as, “May my soul be received into Your hands, spotless and undefiled, as an offering before You.” Her poverty was such that she had nothing appropriate for a winding-sheet, so Gregory doffed a part of his episcopal garb. For the funeral procession, Gregory himself acted as one of the pall-bearers, along with another bishop and two priests (how’s that for an honor guard?). I cannot find any mention of her being the patron saint of anything, which is nuts. I’m sure you will join me in suggesting that she be accounted the patron saint of brothers who revere their older sisters.