I find Heras' storyline doesn't really make sense atm... at least not without a major speculation that isn't revealed yet.
The majority of the game she is portrayed as evil incarnate. Willing to kill her own daughter and Aines best friend, Emma. I can understand her wish to punish the MC because his father killed her husband and child. But apparently she just stopped having the MC bullied by Aine out of the blue. Supposedly that's because Klara.
But that still doesn't add up. In this update she's kind of redeemed. She turns the mafia into a charity and even Jess confirms that she a good person.
So here's where my speculation comes into play... Hera knows far more about the "serum" then we're told. My only guess is Hera used Aine to bully (ie... Torture) the MC so his serum would activate. After that didn't work she gave up on that method and stopped Aine from bullying the MC.
I can only imagine Hera is playing 4d chess... That's the only thing that makes sense. As for her endgame play, we'll have to wait for the great NiiChan to reveal it to us