We did my DD a whole new room in an extension when she was 11/12ish.
She was definitely very, very over cabin beds, which she perceived as babyish. Her request was a double - her room is not massive, so we compromised on a small double. It's an ottoman bed, and so has storage underneath, which is really useful.
Although in her previous room, she had duck egg from 8-11yrs ish, saying she'd outgrown pink, in her new room she picked pink again - but a blush pink, and silver glittery feature wall! (not my choice - a bit blingy for me, but I'm not a teenager!)
She has an IKEA Malm dressing table, with a mirror over it - this also doubles as a desk. She has Malm bedside tables/drawers - these come in lots of different sizes, so are useful for fitting and making the most of odd spaces.
We used an IKEA kids wardrobe (stuva I think?) in plain white, and changed the handles to something more grown up, because these give you drawers underneath, with hanging space above, and utilises the space well. Once the handles are changed, they don't look childish.
So overall, storage and IKEA would probably be my suggestions!
Re paint colour - its cheap and easy to change, so let her choose.