I sometimes blame myself or rethink if there is anything I could have done differently. I pray daily for her heart to turn back to God. What else can parent do?
You're question is going to find 2 types of believers.
One type, puts going to heaven as the Cross you are to bear, and if you mess up, you dont go.
Another type, will tell you that once you belong to God, you belong to God based totally on what Christ has done to cause that to be so as the gift of Salvation.
Here is what i can tell you.
If your adult child was born again, then they are in God's hands.
Its very common that people find doubt and that becomes their faith.
Dead faith, is not dead salvation. Its just a place of mind.
Minds change all the time, Emptyvessel.
Often, doubt that believes no longer, is a seed of real faith being planted.
If you read your NT, you know that a believing wife can rescue an unbelieving husband from their lack of faith, not by beating them with a bible verse and a bible, but simply by maintaining their own faith.
ITs not different with your adult child and you.
We can't beat someone with the Cross and make them believe it.
In fact, the more we push, the more they resist.
What we do is lead and lead, and by example.... And that is best supplied by unconditional love.
The NT says that God saved us when we were UNGODLY......so, that is How God loves us.
We do the same.
Billy Graham, was once asked....>>"what if you found out one of your children was GAY".
He said...."then i would love that one more".
That does not mean he accepted their sexuality, it just means that he would love them more.
Love never fails.