One more thing. While "Miki" can mean the trunk of a tree, beautiful tree wouldn't work because the "ki" kanji for tree in a name tends to be a boys' name and Miki is a girls' name.
Other possible name meanings (based on kanji possibilities):"mi" -beautiful -fruit"ki" -joy -honour/respect/worship -writings -turtle (not so common in modern names, I don't think)Some people add "ko" to Miki. Could add "e" (pronounced ay).