וְלַאֲחֹת֤וֹ הַבְּתוּלָה֙ הַקְּרוֹבָ֣ה אֵלָ֔יו אֲשֶׁ֥ר לֹֽא־הָיְתָ֖ה לְאִ֑ישׁ לָ֖הּ יִטַּמָּֽא׃
O por su hermana virgen, a él cercana, la cual no haya tenido marido, <span class="x" onmousemove="Show('perush','Este es el <b>37mo Precepto Positivo</b> enumerado por el Rambam en el Prefacio a Mishné Torá, su “Compendio de la Ley Hebrea” para todo el Pueblo de Israel.',event);" onmouseout="Close();">por ella se contaminará</span>.
Siftei Chakhamim
But perhaps to a “nesuah.” Meaning that although the plain understanding of הויה [lit. "being" having the connotation of marriage] refers to kiddushin [betrothal], nonetheless, we also find הויה referring to relations as in “his virgin [sister] who is close to him, who was not היתה ["married"] to a man” (Vayikra 21:3) where [היתה] refers to relations, meaning she was a nesuah. Thus, I would have said that הויה here also refers to relations and a she was a nesuah, such that both the father and the husband would annul her vow. However “when it says…”