Relatively little is known about the saint, but the tradition holds that she was a nun whose monastery, located near Monte Cassino, followed the Rule and customs of her brother.
There is a curious sexism at work, it seems to me, in the suggestion of a number of modern (and modernist!) scholars who suggest that the inclusion of St Scholastic in the life of St Benedict is a mere literary device, an invention for teaching purposes. Saints, according to some, are not allowed to have sisters, let alone one's who outshine them in holiness!
St Scholastica visits her brother
The first of the two incidents of her life recorded in St Gregory's Life of St Benedict, though, seems to me to ring particularly true in its nice witness to the fact that even in the saints, sibling rivalry can still be at work! Here is the story (trans Marius Ivascu):
"His [St Benedict's] sister, named Scholastica, was dedicated from her infancy to our Lord. Once a year she came to visit her brother. The man of God went to her not far from the gate of his monastery, at a place that belonged to the Abbey. It was there he would entertain her. Once upon a time she came to visit according to her custom, and her venerable brother with his monks went there to meet her.
They spent the whole day in the praises of God and spiritual talk, and when it was almost night, they dined together. As they were yet sitting at the table, talking of devout matters, it began to get dark. The holy Nun, his sister, entreated him to stay there all night that they might spend it in discoursing of the joys of heaven. By no persuasion, however, would he agree to that, saying that he might not by any means stay all night outside of his Abbey.
At that time, the sky was so clear that no cloud was to be seen. The Nun, hearing this denial of her brother, joined her hands together, laid them on the table, bowed her head on her hands, and prayed to almighty God.
Lifting her head from the table, there fell suddenly such a tempest of lightning and thundering, and such abundance of rain, that neither venerable Benedict, nor his monks that were with him, could put their heads out of doors. The holy Nun, having rested her head on her hands, poured forth such a flood of tears on the table, that she transformed the clear air to a watery sky.
After the end of her devotions, that storm of rain followed; her prayer and the rain so met together, that as she lifted up her head from the table, the thunder began. So it was that in one and the very same instant that she lifted up her head, she brought down the rain.
The man of God, seeing that he could not, in the midst of such thunder and lightning and great abundance of rain return to his Abbey, began to be heavy and to complain to his sister, saying: "God forgive you, what have you done?" She answered him, "I desired you to stay, and you would not hear me; I have desired it of our good Lord, and he has granted my petition. Therefore if you can now depart, in God's name return to your monastery, and leave me here alone."
But the good father, not being able to leave, tarried there against his will where before he would not have stayed willingly. By that means, they watched all night and with spiritual and heavenly talk mutually comforted one another.
Therefore, by this we see, as I said before, that he would have had one thing, but he could not effect it. For if we know the venerable man's mind, there is no question but that he would have had the same fair weather to have continued as it was when he left his monastery. He found, however, that a miracle prevented his desire. A miracle that, by the power of almighty God, a woman's prayers had wrought. Is it not a thing to be marveled at, that a woman, who for a long time had not seen her brother, might do more in that instance than he could? She realized, according to the saying of St. John, "God is charity" [1 John 4:8]. Therefore, as is right, she who loved more, did more."