Certainly, she did. Officially, that was in the 15th century, but if you want to argue that it was previously known, all that can be referred to are a few fleeting comments from early church leaders.....
If it was know to the early church leaders, fleeting or not, then it was known well before the 15th century.
Here are three very relevant quotes from Augustine
Augustine
"The man who has cultivated that remote land and who has gotten his bread by his very great labor is able to suffer this labor to the end of this life. After this life, however, it is not necessary that he suffer. But the man who perhaps has not cultivated the land and has allowed it to be overrun with brambles has in this life the curse of his land on all his works, and after this life he will have either
purgatorial fire or eternal punishment" (
Genesis Defended Against the Manichaeans 2:20:30 [A.D. 389]).
Augustine
"Temporal punishments are suffered by some in this life only, by some after death, by some both here and hereafter, but all of them before that last and strictest judgment. But not all who
suffer temporal punishments after death will come to eternal punishments, which are to follow after that judgment" (
The City of God 21:13 [inter A.D. 413-426]).
Augustine
"That there should be some fire even after this life is not incredible, and it can be inquired into and either be discovered or left hidden whether some of the faithful may be saved, some more slowly and some more quickly in the greater or lesser degree in which they loved the good things that perish, through a certain
purgatorial fire" (
Enchiridion of Faith, Hope, and Love 18:69 [A.D. 421]).
Another very interesting one is this:
In The Martyrdom of Perpetua and Felicity (AD 402) Perpetua describes a vision she had of her brother Dinocrates, seven years dead, and says I saw Dinocrates going out froma gloomy place, where there were several others, and he was parched and very thirsty, with a filthy countenance and pallid colour, and the wound on his face which he had when he died.”….. “For him I had made my prayer, and between him and me there was a large interval, so that neither of us could approach the other…. and knew that my brother was in suffering. But I trusted that my prayer would bring help to his suffering” then later she had a further vision “I saw that the place which I had formerly observed to be in gloom was now bright; and Dinocrates, with a clean body well clad, was finding refreshment…Then I understood that he was translated from the place of punishment”.
There are many examples from the early centuries of praying for the dead. That shows that there was something after death that could happen to a dead person that such prayers could assist with. That could not be heaven (not needed) or hell (could not help).
These are taken from This Rock Magazine May-June 1992
Abercius
"The citizen of a prominent city, I erected this while I lived, that I might have a resting place for my body. Abercius is my name, a disciple of the chaste shepherd who feeds his sheep on the mountains and in the fields, who has great eyes surveying everywhere, who taught me the faithful writings of life. Standing by, I, Abercius, ordered this to be inscribed; truly I was in my seventy-second year. May everyone who is in accord with this and who understands it pray for Abercius" (Epitaph of Abercius [A.D. 180]).
Tertullian
"We offer sacrifices for the dead on their birthday anniversaries" (The Crown 3:3 [A.D. 211]).
Tertullian
"A woman, after the death of her husband...prays for his soul and asks that he may, while waiting, find rest; and that he may share in the first resurrection. And each year, on the anniversary of his death, she offers the sacrifice" (Monogamy 10:1-2 [post A.D. 213]).
Lactantius
"But also, when God will judge the just, it is likewise in fire that he will try them. At that time, they whose sins are uppermost, either because of their gravity or their number, will be drawn together by the fire and will be burned. Those, however, who have been imbued with full justice and maturity of virtue, will not feel that fire; for they have something of God in them which will repel and turn back the strength of the flame" (The Divine Institutions 7:21:6 [inter A.D. 304-310]).
Cyril of Jerusalem
"Then we make mention also of those who have already fallen asleep: first, the patriarchs, prophets, apostles, and martyrs, that through their prayers and supplications God would receive our petition; next, we make mention also of the holy fathers and bishops who have already fallen asleep, and, to put it simply, of all among us who have already fallen asleep, for we believe that it will be of very great benefit to the souls of those for whom the petition is carried up, while this holy and most solemn sacrifice is laid out" (Catechetical Lectures 23:Mystagogic 5:9 [A.D. 350]).
Cyril of Jerusalem
"And I wish to persuade you by an illustration. I know that there are many who are saying this: 'If a soul departs from this world with sins, what does it profit it to be remembered in the prayer?' Well, if a king were to banish certain persons who had offended him, and those intervening for them were to plait a crown and offer it to him on behalf of the ones who were being punished, would he not grant a remission of their penalties? In the same way we too offer prayers to him for those who have fallen asleep, though they be sinners. We do not plait a crown, but offer up Christ who has been sacrificed for our sins; and we thereby propitiate the benevolent God for them as well as for ourselves" (Ibid. 5:10).
Gregory of Nyssa
"If a man distinguish in himself what is peculiarly human from that which is irrational, and if he be on the watch for a life of greater urbanity for himself, in this present life he will purify himself of any evil contracted, overcoming the irrational by reason. If he have inclined to the irrational pressure of the passions, using for the passions the cooperating hide of things irrational, he may afterward in a quite different manner be very much interested in what is better, when, after his departure out of the body, he gains knowledge of the difference between virtue and vice and finds that he is not able to partake of divinity until he has been purged of the filthy contagion in his soul by the purifying fire" (Sermon on the Dead [A.D. 382]).
Epiphanius
"Useful too is the prayer fashioned on their behalf, even if it does not force back the whole of guilty charges laid to them. And it is useful also, because in this world we often stumble either voluntarily or involuntarily, and thus it is a reminder to do better" (Panacea Against All Heresies 75:8 [inter A.D. 374-377]).
John Chrysostom
"Weep for those who die in their wealth and who with all their wealth prepared no consolation for their own souls, who had the power to wash away their sins and did not will to do it. Let us weep for them, let us assist them to the extant of our ability, let us think of some assistance for them, small as it may be, yet let us somehow assist them. But how, and in what way? By praying for them and by entreating others to pray for them, by constantly giving alms to the poor on their behalf. Not in vain was it decreed by the apostles that in the awesome mysteries remembrance should be made of the departed. They knew that here there was much gain for them, much benefit. When the entire people stands with hands uplifted, a priestly assembly, and that awesome sacrificial Victim is laid out, how, when we are calling upon God, should we not succeed in their defense? But this is done for those who have departed in the faith, while even the catechumens are not reckoned as worthy of this consolation, but are deprived of every means of assistance except one. And what is that? We may give alms to the poor on their behalf" (Homilies on the Epistle to the Philippians 3:9-10 [inter A.D. 398-404]).
Contd. next post