Heresay - now that's a different matter.
Absolutely. So is hearsay.
I cannot prove a negative. No one has proven she was a nun. Even if what she says is accepted as true, she was never a nun.
As far as I know there are only two written sources which are "infallible" sources of Catholic teaching:
Catechism of the Catholic Church
924 "As with other forms of consecrated life," the order of virgins establishes the woman living in the world (or the nun) in prayer, penance, service of her brethren, and apostolic activity, according to the state of life and spiritual gifts given to her. Consecrated virgins can form themselves into associations to observe their commitment more faithfully.
The single reference to "nun" found in the Catechism.
CODE OF CANON LAW
Though there are several references to "nun" there are none which identifies how one becomes a nun.
You are among those who say she is a fake or, at the least, was not a nun. The burden of proof is really on you to prove your claims.
I will not ask for that proof. I am certain there are those, possibly even you, who have engaged in a frantic search to find that proof and have come up with nothing, otherwise we would have seen it posted.
I don't think it reasonable to ask for that level of proof. Rather all I ask is for the "official", "infallible" definition of what a "nun" is and the requirements which must be met before one can call herself a "nun". Easy isn't it?