There is almost certainly no way to know for certain. Efforts to chase down the origins of contemporary "urban folklore" have almost always failed. The repetition of names - one for the English monarch and the other for the "malevolent spirit in the mirror" - is likely not a coincidence. That does not mean that the point(s) of origin and/or those who repeated the modern story of Bloody Mary were even aware of the monarch. The term, after all, is part of the common vocabulary because of the morning drink. The idea of a murderous Tudor monarch having the same name could have and probably occasionally did put wind in the sail of the modern expression of folklore, but I doubt the point(s) of origin necessarily started with the English queen. In short, I suspect that the urban folklore began with a name that was, in itself, thrilling and evocative of something powerful (the history of the queen aside).

I discuss the question of origin when it comes to modern elements of folklore in my Introduction to Folklore:

The answer to this question is somewhere between "we don't know" and "it's just what people do" – that is, they invent these sorts of stories. Several folklorists, including the late Alan Dundes and Jan Harold Brunvand, recognized an opportunity with recent urban legends to finally track down "the source," the point of creation, to better understand how stories originate. For the most part, they were unable to find the point/person of origin to any general degree of satisfaction. It is a maddening question, and much like the proverbial chicken and the egg, it isn't likely to be resolved.

People tell stories. People repeat stories. And as they repeat them, people modify stories, which sometimes results in the birth of new stories. There might have been some highly imaginative, creative people who invented stories at some point, but that sort of person has yet to be identified in the annals of folklore studies. Folklorists often asked renowned storytellers to tell a new story, to invent something that they had not heard. Without exception, these requests were refused by the storytellers who explained that while they repeated stories, they did not invent them. In general, it may be best to consider the possibility that the process of repetition and transmission is the source of much of the creativity that is evidenced in the international library of oral tradition.

One example may help shed light on the creative process: the Cornish droll tellers were known for their wild adaptation of the material they heard. Their counterparts in Ireland were the seanchaithe, professional storytellers who prided themselves in the faithful recitation of stories they had heard, as close to the original as possible. Perhaps in this, we can see the opportunity for new stories to be born, and indeed, Cornish oral tradition includes more than its fair share of distinct subtypes (i.e. variants) of legends and folktales, perhaps offering a hint as to how these things may come into existence.