She didn't the first time around. She did it at her second chance because it's necessary to absolutely cut off ties if she want to help Cedric become emperor.
She doesn’t did that just because she wants to help cedric, she also did that for herself. She didn’t do it in her first life cuz she thought there will be a chance for her to get loved by her own mother by helping her brother. Cuz she loves her mother. And thats what an abuse children feels. we want to get a chance. even though that just a dreams. But reality is suck. And tia realizes about it... she even said “family is just sweet fantasy.” That means she realizes already how toxic her family is and dreaming about a chance wont benefit her anything.
on behalf of children all around the world who raised by a narcissistic mother like me, I proudly say “CONGRATULATIONS ” to our main character tia, cuz she really cut the ties with her toxic mother that I couldn’t even dare to do it in real life hahahahaha