Aibu to suggest alternative books to 12 year old DD when she asks to read something I believe is unsuitable for her age?

Just let her read anything she wants to read. She can probably get a copy in her school library to read in her lunch break if you say no or go to town and read it in the library. The good thing is she is reading.

I was an avid reader of anything as a child. Charles dickens, all the classics, Agatha Christie’s 8 onwards. Then Stephen kings from 10 or younger onwards . My safe place are books and they got me through my childhood. I still reread Agatha Christie and Stephen King to feel safe during bad periods in my life.

I’m off to read a chapter or two before bed now.

Same.
I read my mother's Casteel saga collection and became hooked on VA. I bloody loved the drama. I'm 37 now and I might read them again.

She is going to read it regardless so I think the better option is to do it with consent so that she knows she can talk to you if anything unsettles her.

My dd is nearly 13 and has been reading adult books for a long while. She loves a good murder mystery.

Oh God I remember my mum giving me her copy of Flowers on the attic. I was about 12. I’d forgotten all about that!

Throne of glass has much much less romance and if I remember correctly virtually no sex but it does have much much more violence and torture etc.

it’s a series of books.

My mum gave me that to read at 12. To be fair she never censored anything I read and I still read a lot

I read Flowers in the Attic at 12, (secretly, my friend had read her older sister’s copy and leant it to me). So I think she’ll cope. Wish I’d left it a couple of years though!

It’s tricky because 12 sounds so young, and yet I was also a voracious reader at that age and definitely read books with sex, rape, murder, etc. which didn’t phase me at all. I think your idea of introducing her to young adult fantasy fiction that contains romantic/sexual themes without being too explicit is a good one - I would suggest the Matched trilogy by Ally Condie and Delirium by Lauren Oliver.

My generation read Flowers in the Attic at that age.

This seems relatively ok in comparison.

ACOTAR is part of a series. From what I remember it’s not too raunchy but the following ones made me blush. ( I adored them all though!). Lots of violence and some coercive control type aspects ( from what I remember). Lots of sex in the later books.

ETA I’ve googled and it’s not actually classed as a YA book.

The Contender series by Taran Matharu are a bit Hunger Games ish. But, in our opinion, his Summoner series was way better - although it's a different style to your DD's other books.

I let my kids read anything they choose. My daughter read a good girls guide to murder when she was 12 - and she is very young for her age so i thought she’d hate it. I tell them all the time that they can ask me anything they aren’t sure about or come to me if anything worries them and im glad they’re exploring a bit now while they’re young enough to come to me with questions. And some of their questions are quite interesting (and sometimes hilarious!)

Honestly they’ll likely have all this stuff in the school library anyway so you can’t really stop her - that’s where my daughter found the good girls guide books originally.

Offer alternatives and have a discussion about why you think it is unsuitable. I read some books my DD wanted to read to see if I thought they were mature enough.
As I remember she read the Red Queen books but also started reading some classics like the Brontes ,etc

Apparently (according to DD15) Sarah J Maas wrote a series starting with Throne of Glass and the first couple of books in the series are ok. However, later ones are closer to ACOTAR so not as suitable.

I dunno about adult books.

they’ve got quite a lot of romance in them and some moderately detailed sex scenes.
it’s made quite clear that the bad things are done by bad people and (at least some of them) get their comeuppance.