Malachi Martin, unfortunately, was a teller of tall tales ... and can't be trusted. I'm not sure how exactly he was offering a Mass of reparation when he had been laicized and therefore had no business offering Mass. There are also reports that he was living with a mistress.
I knew someone at STAS who went a couple talks in a series of lectures being given by Malachi Martin. He told me that one was to a group of mostly SSPX types and another to a group of Feeneyites. During the first talk, he declared that Archbishop Lefebvre was the greatest theologian of the 20th century, while in the second talk he said the same thing of Father Feeney.
Reportedly Martin was working for Cardinal Bea digging up dirt on the attendees at Vatican II so they could blackmail them into doing what they wanted.
So this "Agnes" who was tracked down evidently stated that this ritual took place in 1957, not in 1963 as Martin claimed.
I could be wrong, but I was thinking that Fr Martin was never technically "laicized", rather, he was on some sort of indefinite leave, and thus could have celebrated Holy Mass at his discretion. The way I heard it, he was buried alongside a woman simply because he had no money to buy a funeral plot of his own, and she gave him one of hers. He gave almost all of his money to poor seminarians and lived frugally. Supposedly she was just a friend, and in charity and reverence towards a priest of God, I will not challenge that.
I actually spoke with him briefly one time, I was trying to organize a lecture for a group, and he was recovering from a heart attack, so he could not come. I'll never forget that he bellowed into the phone "who gave you my number?".
He was kind of ticked until I explained. I have to look back and chuckle about that one.
"Tall tales" are better suited for things such as deep-sea fishing and hunting in the wilderness for wild boar.