Sue Snell says "Only a few of us survived. We never talk about that night."
Who were the other survivors? I thought she was the only survivor from that prom night?
"Our country, our rules. Okay?"
-Frances O' Brien
Probably just people who happened to be outside (smoking, fooling around in the car etc.) when Carrie went nuts.
"Well...I've seen enough. Come on Charlie, we're going home."
I felt like the Sheriff was also a survivor.
"Cinema is everything to me. I live and breathe films -- I even eat them!"
- Lucio Fulci
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It was implied that Sue was the only one who survived, but they didn't actually say that. Remember, the fire truck was arriving as Carrie left the prom. They could have put the fire out and then there were some survivors. Sue's mother said, "With Tommy and all the others gone, it's best we just get away for a while." I think she just meant all of Sue's friends and acquaintances were gone. Chris, Norma, etc.
By the way, Sue's mother in Carrie 1 is her real mother! And her sister Katie is the girl that sang the two songs at the prom.