Grace saves us.
First, you have to learn what God's grace (not Mary's) is...Then you have to find out why it is...
Grace does not save anyone...Grace is graciousness, favor, (unmerited favor)...Grace allows us to be saved without giving something in return...
We are saved because of faith as opposed to being saved because of works...That's what the grace is...
Rom 11:6 And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then is it no more grace: otherwise work is no more work.
Because of God's graciousness (grace), Jesus gives us the free gift of salvation when we have faith (trust) in him...
Really it is God Who saves by Grace through faith. Been like that since the beginning. First clear example is Noah, which is what Peter was explaining in 1 Peter 3.
But I know what you were saying. It is called the Gospel of Grace for a reason. What Christ Jesus did for us was the greatest act of love.
Romans 5:8-11 KJV
But God commendeth his love toward us, in that, while we were yet sinners, Christ died for us. Much more then, being now justified by his blood, we shall be saved from wrath through him. For if, when we were enemies, we were reconciled to God by the death of his Son, much more, being reconciled, we shall be saved by his life. And not only so, but we also joy in God through our Lord Jesus Christ, by whom we have now received the atonement.