Goodnight Mr Tom terrified me as a child. I loved it, I still do, but the mother was genuinely frightening and I remember crying over the way she treated Will. I read that at your daughter's age and found it challenging. My mum and I discussed it together and watched the film, which helped a lot (though even now I still find the mother's portrayal in the film very upsetting)
I'm trying to think of particular parts of Angela's Ashes that would be upsetting or disturbing. There is some discussion of sex but it's spoken about in a very naive manner that shouldn't be confusing to a nine year old. Certainly I first picked it up at 11 or so and understood what they were discussing. The themes around infant death might be upsetting however they are encountered in books designed for children/teens such as Vicky Angel, The Cat Mummy (both Jacqueline Wilson) are in many ways handled more tastefully in Angela's Ashes.
I must admit parts did upset me a bit at eleven but that was because I am Catholic and I took parts a bit too literally. If you aren't Catholic or indeed Protestant, it might not resonate so deeply and so you'd struggle with it less.
I wouldn't call it misery memoir. There's a world of difference. It's actually a very uplifting story. The film is fantastic, if she reads it then definitely give the film a go in time (it's a fifteen because of swearing and occasional mild reference to sex and masturbation, and death in infancy)
Be proud that she's reading proper material. Keep her on that track with good books - why not try To Kill a Mockingbird, Pollyanna, What Katy Did, Heidi, Laura Ingalls Wilder, etc.