A Sefer Torah fell by accident from the hands of a congregant, are the women obligated to fast?
Although it is customary for anybody in the presence of a Sefer Torah falling on the floor to fast, women are not obligated to follow this custom. Generally today, when people are weak and it is difficult for them to fast, tzedakah can be given in place of fasting.
The actual obligation to fast applies specifically to the person from whose hands the Sefer Torah fell.
See Magen Avraham 44:5; for a detailed explanation, see Iggros Moshe 3:3; Tzitz Eliezer 5:1. See also Birkei Yosef, Yoreh De’ah 282; Shut Divrei Chaim Yoreh De’ah 59; Imrei Eish 6; Teshuvos Vehanhagos 3:169.