One of our new RCIA converts has a mother who is SDA. She sends her daugher lots of books and pamphlets to disuade her to leave this church of Satan. I copied her leaflets from the Catholic answers website. What else can I do to help her respond to her mother?
By “SDA” I assume you are referring to “Seventh-Day Adventist.” However, without a specific example of what your friend is dealing with, I cannot give you very specific advice.
As the only complaint you mentioned that your friend has is her mother attempting to get her to leave “this church of Satan [the Catholic Church],” then what I can suggest is that your friend return all materials received to her mother explaining, respectfully, that discussion on the issues is not possible until ground rules for discussion are set. In this case, she might explain that she wants to set a ground rule that her religion may not be called satanic as Catholics do not worship the devil, and be open to any reasonable ground rules her mother wishes to suggest.
A good book for help in dealing with difficult people in a charitable and Christian manner is Gregory Popcak’s God Help Me! These People Are Driving Me Nuts: