Early Quenya
heresse
noun. sister
hestani
noun. sister
hestanoini
noun. sister
hestaqin
noun. sister
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A word for “sister” in the Qenya Lexicon of the 1910s with numerous variants: heresse, hesta(noi)ni, and hestaqin, all based on the early root ᴱ√HESE that was the basis for “brother” and “sister” words (QL/40). Of these Tolkien said heresse was the “ordinary word”, and it also appeared in the Poetic and Mythological Words of Eldarissa (PME/40).