I think, especially after Carrie got the gym teacher's support and sympathy, Carrie started to seem like a martyr. That meant Chris H would have had to start seeing herself as DEFINITELY being the bad girl, and the human mind just doesn't work that way. She couldn't see herself as being wrong, so she had to believe that Carrie was just a bee-yotch, or a holier than thou (insert bad word that starts with c). So, she had to just get meaner and meaner and meaner to Carrie.
For Grave Encounters I'm Lance Preston.

She got slapped one too many times.

I think because Carrie was easy to pick on and others were doing so too. Also the gym teacher gave them extra classes as punishment because they had been bullying Carrie (shower scene). It was easier to get revenge on Carrie than on the teacher, at least that's what Chris thought. And also yeah a dumb chick she was.

Thanks Johan, I thought she got killed. It's a good point though why PJ Soles didn't get angrier at the gym teacher but took it out on poor Carrie. I liked that movie a fair bit because Sissy Spackeck engendered so much empathy. Great actor and she was also excellent in Terence Malick's
Badlands
, an account of the spree killer Charles Starkweather.

She died in the movie I'm sure of that. I believe she got hit by a table and thrown against the wall ending in death and if not she got burnt up.

That's an excellent point. I never thought of that. Fkcn gym teacher I wanted her to get burnt up. Hang on didn't she get burnt up in the movie brah or did she excape amirite.

IIRC, in the book she tries to get the gym teacher fired and it backfires. Either way, she was a dumb, spoiled bitch who would blame anyone but herself.
Kieran is a retcon. Audrey was Piper's original partner.