In some translations of her treatises and Dialogue, the sins referred by Christ regarding His priests point to the fact that if these men said the Mass properly, not mumbling, they knew that they would be creating a sacrilege.
Some things have not changed, but we should be so scandalized....
"The fruits of this death-giving tree, are as diverse as sins are diverse. See that some of these fruits are the food of beasts who live impurely, using their body and their mind like a swine who wallows in mud, for in the same way they wallow in the mire of sensuality.
"Oh, ugly soul, where have you left your dignity? You were made sister to the angels, and now you are become a brute beast. To such misery come sinners, notwithstanding that they are sustained by Me, who am Supreme Purity, notwithstanding that the very devils, whose friends and servants they have become, cannot endure the sight of such filthy actions.
"Neither does any sin, abominable as it may be, take away the light of the intellect from man, so much as does this one. This the philosophers knew, not by the light of grace, because they had it not, but because nature gave them the light to know that this sin obscured the intellect, and for that reason they preserved themselves in continence the better to study.
"Thus also they flung away their riches in order that the thought of them should not occupy their heart. Not so does the ignorant and false Christian, who has lost grace by sin."
"What I say of the universal body and the mystical body of the Holy Church (that is to say the Christian religion) I also say of My ministers, who stand and feed at the breasts of Holy Church; and, not only should they feed themselves, but it is also their duty to feed and hold to those breasts the universal body of Christian people, and also any other people who should wish to leave the darkness of their infidelity, and bind themselves as members to My Church.
"See then with what ignorance and darkness, and ingratitude, are administered, and with what filthy hands are handled this glorious milk and blood of My spouse, and with what presumption and irreverence they are received. Wherefore, that which really gives life, often gives, through the defects of those who receive it, death; that is to say, the precious Blood of My only-begotten Son, which destroyed death and darkness, and gave life and truth, and confounded falsehood.
"For I give this Blood and use It for salvation and perfection in the case of that man who disposes himself properly to receive it, for It gives life and adorns the soul with every grace, in proportion to the disposition and affection of him who receives It; similarly It gives death to him who receives It unworthily, living in iniquity and in the darkness of mortal sin; to him, I say, It gives death and not life; not through defect of the Blood, nor through defect of the minister, though there might be great evil in him, because his evil would not spoil nor defile the Blood nor diminish Its grace and virtue, nor does an evil minister do harm to him to whom he gives the Blood, but to himself he does the harm of guilt, which will be followed by punishment, unless he correct himself with contrition and repentance.
And one of her letters to the Pope Gregory XI in Avignon: http://www.britannica.com/women/article-9404147