Why did God create Eve from Adam’s rib instead of a different bone?
The biblical account of Eve being taken from Adam’s rib is completely allegorical. One may interpret the allegory in various different ways, but as far as I know there is no official interpretation of the allegory. The fact of the matter is that Eve was born as an infant from two parents in exactly the same manner that you and I were born. And Brigham Young has stated that no person was ever made on any other principle—
“Though we have it in history that our father Adam was made of the dust of this earth, and that he knew nothing about his God previous to being made here, yet it is not so; and when we learn the truth we shall see and understand that he helped to make this world, and was the chief manager in that operation. He was the person who brought the animals and the seeds from other planets to this world, and brought a wife with him and stayed here. You may read and believe what you please as to what is found written in the Bible. Adam was made from the dust of an earth, but not from the dust of this earth. He was made as you and I are made, and no person was ever made upon any other principle” (Journal of Discourses, 26 vols., 3:, p.319).
So Adam and Eve were born on another world, undoubtedly a terrestrial kingdom, as that is the state they and the world were in until the fall, when they were expelled from the Garden, were transformed to mortal beings, the earth being changed from a terrestrial to a telestial kingdom.