I just hate yelling, period. I grew up in a household where NO ONE yelled, or at least is was very rare. My mom has always said that there's no reason to yell at anyone, unless they're stepping off a curb and there's a car coming. When someone yells at you, your fight or flight instinct kicks in and you stop listening. I know that, when someone yells at or even near me, my ears start buzzing and I can't deal. It's not an effective way to communicate.
I had many dance teachers over the years and the only reason for even a raised voice was to be heard over the music. I would never allow someone to speak to me or my young child the way Abby speaks to everyone in her life. The things she says to those children aren't things that should even be said to an adult. It's like no one taught her tact or manners at all. She seems to have no edit button and no awareness of how horrid she is to those little girls, not to mention everyone else.
Abby seems like a very alone person to me. I know the show is about her dance studio, but we don't ever see anyone who is close to her in her personal life. We know she's got a mother, but there aren't any other family members or friends around her. It's kind of sad.