Tia elicits the feeling of pity and one becomes sympathetic to her unfair situation. It's makes her a heroic villainess in my eyes. She is doing stuff for the greater good, for the people she cares about, she has a moral compass that's guiding her onto the path of good and compassion. She doesn't manipulate people to get her way, she didn't plan on Cendric's reaction. She's only a villainess to those who wish to do her harm and those who want to use her for some kind of gain.
However...
Aria is a boss *ss b*tch who will get hers, with smart planning and economic stability and one becomes empathetic to her situation. I feel no pity for Aria, she exudes strength without compassion for others. Everything she does is for the sole benefit of herself because she is cunning and calculating. She knew how the maids would react if she gave them something expensive, she did it before with Annie... She is a villainess through and through, she threw tantrums when she didn't get her way and she destroyed others belongings. She was a brat from the beginning.
Though both of their circumstances are understandable, how you feel about Tia and Aria will differ as
Aria is calculating and manipulative, she only does things that benefits "me, myself, and I", anything else is a byproduct. Ffs she takes pleasure in tormenting Millie. So far her every action has furthered her plot for revenge and economic stability, not
necessarily righting a wrong.
Tia is self sacrificing and a heroic "villainess". She actually cares for those around her and has people within the story who are sympathetic to her situation, people she can lean on because she's ultimately good. Some of her "villainess" actions don't even make her happy...
Tl
R- Tia is good "villainess", Aria is an actual villainess