Idhā creates a temporal conditional relationship, approximately “whenever.” Qāmatā, from qāma–yaqūmu, is a third-person feminine dual perfect. Its ending marks feminine reference and dual number.
Taḍawwaʿa al-misk describes what followed. Both qāmatā and minhumā refer to two women, whereas al-misk is the separate singular masculine subject of taḍawwaʿa.
Number and gender matter in translation: “the two women rose” and “from them both” are more accurate than singular equivalents.