I remember going to see Jurassic Park (the first one) when I was 20. I jumped out of my skin several times. There was a little girl abput 5 sat next to me with her mum who loved it and was far less scared than me!
The same things don't scare the same people. Both my DSs watched Doctor Who from a young age, 3 or 4. But I knew some kids who were scared by it at 9 or 10. Equally DS1 went to the cinema aged 15 or so to watch The Woman in Black and was terrified.
But if you watch Marvel and DC films regularly you know there is violence but it's quite stylised. There's not much gore because they're all superheros so they don't really get injured!
OP if she sits quietly and can do so for the best part of 3 hours, and wont be frightened, then yes take her. I don't see the big deal. We're going to see it tomorrow night...can't wait!