I'm not going to dispute your husband's cousin's sincerety. The issue from a Protestant perspective boils down to a matter of grace and grace alone.
The wages of sin are death
From an entirely Scriptural perspective grace is the act of unmerited benifacting.
From an entirely Scriptural perspective, mercy is an act of unmerited reprival of penalty due to merited justice.
Jno 3:16 tells us what?
Believe. Grace is a simple concept which is difficult to grasp. We cannot earn it, nor do we deserve it. You cannot understand Grace until you understand it is not deserved. People make God's Grace to us complicated, it is not.