Well, it would have scared the living daylights out of me at 7, but so would the first 6! The seventh film includes such things as [spoilers!]:
- a woman suspended, looking as if she were in pain, above a table of evil guys while they talk. She's then killed with a curse, and it's implied a large snake is going to eat her (you don't see it).
- a very creepy (IMO!) scene where Harry and Hermione follow an old lady to a house; she doesn't speak, it's dark, there's a room full of maggots, flies and what looks like blood, and the woman morphs into a snake and attacks the kids. There's one scary jump shot in the fight scene where the snake suddenly lunges upwards.
- a "ghost" of Dumbledore forms out of dust in a house and runs screaming at the children before vanishing - it's a booby trap
- one non-human character gets stabbed to death by a flung dagger in the chest
- one character carves a word into another's arm, to torture her - we don't see the carving directly, but we hear the screaming and see the word afterwards
- one character splits open another's grave - we see the corpse, but it isn't gory-looking. he just looks asleep
- Dementors chase characters and scrabble to reach them through a grille
- One character nearly drowns (because of magic) in a dark pond under the ice
- Voldemort appears close to Harry and tries to kill him with a spell
- there are several newspaper references to Muggles being killed, witches being captured and so on
-one character gets a disfiguring head wound
That's the stuff that leaps out of me, but really, the whole film is about being chased, being in hiding, feeling lost and frightened while evil gains power in a rather blatantly Nazi-like way. It's dark. It's meant to be. Now, compared to the NEXT film, where the trailer shows the bodies of children strewn around? It might be a barrel of roses. So if you're prepared to let her watch this one, remember she'll only fight harder to see the last one (understandably). And if you haven't read the last book... there are some beloved characters who don't make it. JK Rowling wrote the first book for kids older than seven, and the books get darker and more mature as they go along, as if she were writing to the original audience as they grew up. So don't think "children's book".
On the other hand, if your DD has already seen the previous six and wasn't traumatised, well, I dunno! I thought some of those were pretty darn dark. So she might be OK. And I can certainly sympathise with her wanting to complete the series!