We do not have the original manuscript for the word father. Oliver Cowdery initially wrote fathers in the printer’s manuscript, probably because the use of the double genitive (as in “a remarkable vision of her father’s”) is highly expected by English speakers. In accord with his writing habits, Oliver did not supply the apostrophe for the possessive s. In this instance, he immediately corrected the form fathers by erasing the possessive s. The original manuscript undoubtedly had the more difficult nonpossessive form father in “a remarkable vision of her father”.
In the manuscripts Oliver Cowdery often added a possessive s to nouns, especially names, in constructions involving the preposition of, thus creating instances of the double genitive. Yet there is also evidence for actual double genitives in the original text. See under Alma 46:24 for a complete discussion of this issue. Here in Alma 19:16 the critical text will accept Oliver’s immediate correction in 𝓟 to “a remarkable vision of her father”.
Summary: Maintain in Alma 19:16 the corrected reading in 𝓟 for the genitive construction “a remarkable vision of her father” rather than the double genitive “a remarkable vision of her father’s”, which is what Oliver Cowdery initially wrote in 𝓟 (but without the apostrophe).