I left the Mormon church when I was 15 years old. There were simply too many fundamental things (for me at least) that were wrong about that church, so that even at 15 I knew it would not work out.L.M, it was precisely because my family is so connected with the church that I felt it necessary to resign formally and get my name removed. I wrote the family a brief letter to let them know what was happening, explained that I no longer believed without going into any specific details, and told them all I still loved them.
However, my family continues to be Mormon, especially my mother who invites the missionaries over for dinner. They are not bad people, and I even cooked for them. But over and over they try to press me to come back to the church, to events, to read The Book of Mormon etc. etc. Every time they do this, I say "thank you, but I left the church and never regretted that decision." Now, they are sending visiting teachers, and want to call me to set up a time to discuss these issues.
I try to be nice for the sake of my family, and because they are not the worst people on earth, but they can't get the picture! Why can't Mormons let go???
If your family can't respect your boundaries, cite their 11th Article of Faith: "We claim the privilege of worshiping Almighty God according to the dictates of our own conscience, and allow all men the same privilege, let them worship how, where, or what they may." Or better yet tell them you've left the church but the church won't leave you alone. ;)
That's a pretty myopic view. Calling someone a "child of God [who] falls away to unbelief" is not helpful. Nor is it OK that the missionaries continue to disrespect others because it's "their job." The LDS church isn't really good at honoring people's personal boundaries, from proselyting to visiting teachers to "worthiness" interviews to "discussing the affairs of members constantly." She doesn't believe. Let. it. go.