I am scheduled to go to the Mikvah, be”H, this coming Wednesday night – right after taanis esther. The way I usually go about preparing is to take a bath during the afternoon hours and then, at the mikvah, just do the shower and tevilah. Am I allowed to do the same (bath in the afternoon) if it’s a taanis?
It is permitted for you to do all he regular preparations. This is for two reasons. The chumra of not taking a shower on a taanis only applies to the three fast days with mourning over the Bais Hamikdash, but not on Taanis Esther. The second reason is that this chumra does not apply to a woman doing her preparation for the mikvah
M:B Shar Hatzion 550-8, in the name of Ateres Zieinim, that this applies to the 3 taaneisim, ( Tzom Gidalia, Asara B’teves, Shiva Asar B’tammuz, and not to four taaneisim, also see Kovetz Halachos ( Purim) 2-11, Piskei Teshuvos 550-6 in the name of Kasav sofer O:CH 100.