Seamus- in fairness to the op, the 12A rating is open to interpretation and left to the discretion of parents. You have made your judgment as a parent. She has made hers.
Not every kid is the same. What scares one child won't take a flinch out of another. If you watched an 80s pg movie now (Ghostbusters for example) your jaw would drop at some of the content. Did it scare kids? Some. Others loved it.
My nephew is 9 as is my ds. Dn gets terrified at most movies, including u rated ones. Ds has never been scared during a movie. Ever.
My other ds is 6. He's the same. In fact, the only movie scene he has ever been scared at was (of all things) Stuart Little, when he was about 2. You know the bit where he ends up in the washing machine? Ds wouldn't get into the bath for 2 weeks without freaking out, lol. But just today his swimming teacher was saying he's going to fly through level 3. So, you know, no harm done, lol.