My Mother Will Baptize Herself On The Adventist Church

Hello, I'm an early-converted catholic; I converted last year, around the middle of it.

My mother has always been catholic, sure, she was not only catholic, she made part of the "Carismática" movement (I don't know the term in english), and since my stepfather stepped into our lives she was convinced by him to join the adventist church with him

My mother is going to the adventist church every saturday for the last months (~6 or 7 months) and she is thinking about baptizing herself on this heretic church. What should I do about it? What should I think about it? I'm quite confused about this

(Btw sorry if my english is bad, I'm brazilian and my native language is not english)