These are not isekai though.. they're rebirth.. :3
Shadow Queen
The Villainess Lives Twice
The Villainess Reverses the Hourglass
thank you. also rebirth and turning back time and stuff is fine.
personal favourites
http://www.mangago.me/read-manga/the_justice_of_villainous_woman/
http://www.mangago.me/read-manga/charlotte_has_five_disciples/?1bEl
http://www.mangago.me/read-manga/la_dolce_vita_di_adelaide/?wVN6
http://www.mangago.me/read-manga/they_say_i_was_born_a_king_s_daughter/?wp38
http://www.mangago.me/read-manga/reminiscence_adonis/
http://www.mangago.me/read-manga/otome_game_no_hametsu_flag_shika_nai_akuyaku_reijou_ni_tensei_shite_shimatta/
isekai about the villainess that doesn’t become a good person in a day and like- they actually want to be a villainess and not a second protagonist.