[Psa 127:3 NASB] 3 Behold, children are a gift of the LORD,The fruit of the womb is a reward.
[Pro 22:6 NASB] 6 Train up a child in the way he should go,Even when he is old he will not depart from it.
[1Pe 3:4 NASB] 4 but let it be the hidden person of the heart, with the imperishable quality of a gentle and quiet spirit, which is precious in the sight of God.
This way you might use this name not only as an endearment, but also in its use be reminded how God has gifted you in her and you are responsible for bringing them up in His ways. (Hear, my son, your father's instruction And do not forsake your mother's teaching ("You shall teach them diligently to your sons and shall talk of them when you sit in your house and when you walk by the way and when you lie down and when you rise up.")
You have given the child a birth name which will hold significance all the days of her life. With what you would call a "pet name", which is really meant to be I hope your way of saying a special name between you and her. As we all will receive who overcome (Revelation 2:27). This she will remember and when hearing it will always associate it as something special between you and her. So let it have a significance that far outways the initial intent. That one day you might explain to her why you call her that.
So whatever name you decide to call her that is between you and her. Let it hold meaning that will work both ways in reminding you that you have truly been gifted and that this child that God has entrusted you with will be brought up in His Way and in Knowledge of His Word. To this child it will also hold meaning. One day she'll know that Mom has given me a name that can be found in the Word of God and that my mother loves me!
With the Love of Christ Jesus dear sister @LorineNied .