How is Delores a villain?
Remember her power is super hearing... "She can hear this whole chorus a mile away"
Sabotaging Isbella's love life
Bruno's prophecy for her was "The man of my dreams would be just out of reach.... Betrothed to another" The second time she sings it she includes the added lines "And I'm fine. And I'm fine. And I'm fine. And I'm fine." indicating she's not fine with this.
When Abuela asks if there is a date with Mariano for Isbella that nigh she replies "Tonight. He wants five babies" which shows a scared look on Isbella's face while Dolores gives her a smirk and a side eye.
At the proposal dinner, Dolores starts telling everyone that Mirabel found Bruno's vision, thus causing dinner to erupt in chaos.
Heartless exposure of Mirabel's lack of a gift
In the opening song, Mirabel is clearly uncomfortable telling the kids she doesn't have a gift... a song that Dolores heard all of. At the end of the song, she pops out of no where and says "Mirabel doesn't have a gift" shrugs and walks away.
Gaslighting Mirabel
Mirabel is made a fool at Antonio's gift ceremony when she claims the house is cracking. It is later shown that this is indeed true as Bruno has been patching the walls... Dolores can her a pin drop and an eye twitch, she would have heard the audible cracking of the house and could have backed up Mirabel but instead fainted ignorance.
She knows Bruno is in the walls and doesn't tell anyone!
In the song we don't talk about Bruno, she literally says "I can hear him now" also in the finale song "I knew he never left, I heard him every day" yet fails to mention that her mentally unstable uncle is in the walls and probably needs some help... for like a decade!
She is sad on the final Casita door...
Look at this door and tell me Dolores is happy that everything is back to normal...
I rest my case... (Also, this isn't my theory, but I think it is super funny
)