Section 25 of the Doctrine and Covenants designates Emma Smith as an elect lady and gives her encouragement and assignments. She was instrumental in the translation of the Book of Mormon as she acted as a scribe and supported Joseph Smith in his work.
D&C 25 Overview
“Doctrines of Faith and Hope Found in Emma Smith’s 1835 Hymnbook,” Mary D. Poulter, BYU Studies, Vol. 37, no. 2
Emma Smith was assigned to compile hymn texts for the first LDS hymn book, A Collection of Sacred Hymns, for the Church of the Latter Day Saints. The texts she chose provide a window through which we can view the hopes, beliefs, and convictions of the early Latter-day Saints. Featured doctrines are agency, evangelism, baptism by immersion, the Second Coming and the Millennium, the Creation, the Restoration, and the City of Enoch and the establishment of Zion.
Emma’s Role as a Scribe for the Book of Mormon
“Joseph Knight’s Recollection of Early Mormon History,” Dean Jessee, BYU Studies, Vol. 17, no. 1
Joseph Knight recorded that when Joseph Smith “drew off” the characters from the plates so that Martin Harris could take them to scholars, it was Emma who helped him:
“He now Began to be anxious to git them translated. He therefore with his wife Drew of[f] the Caricters exactley like the ancient and sent Martin Harris to see if he Could git them Translated.”
After Joseph had to give up the plates and interpreters, he in time received them back and Emma was a scribe. Joseph Knight wrote about this time period:
“Now he could not translate but little being poor and nobody to write for him but his wife and she could not do much and take care of her house and he being poor and no means to live but work. His wifes father and familey ware all against him and would not h[e]lp him.”
“Lucy Mack Smith, History, 1844-1845,” p. 11, book 7, at JosephSmithPapers.org
Lucy Mack Smith records that after Joseph lost the plates and interpreters, he supplicated the Lord to get them back, and Emma wrote for him:
“I continued said Joseph my suplications to God without cessation that his mercy might again be exercised towards me and on the 22 of September  I had the Joy and satisfaction of again receiving the record <urim and Thummin> into my possession and I have commenced translating and Emma writes for me.”
“The Coming Forth of the Book of Mormon,” chapter [available as PDF for $5 or ebook for $4.99] in Opening the Heavens, John W. Welch [available in print for $21.95 or ebook for $11.99 or $19.95] This chapter gives verifiable details about the translation process: Joseph and Emma borrowed Joseph Knight’s carriage to go after midnight on Sept. 21-22, 1827, to receive the plates from Moroni; Emma often acted as scribe; Emma gave six statements about the translation, all included here.