Firstly, how old is DD?
I am assuming this is for her bedroom and it is possibly the only room in the house that is exclusively hers.
Why can't she have it on all 4 walls? Once furniture is in etc it won't be as bright if that is what you are worried about.
I painted my son's room lime green, it looked like some sort of nuclear disaster site
but once the furniture was in, noticeboard, stickers etc it was great and didn't feel as bright.
But then I go off the duvet cover, and pick a colour from that. So he had a navy blue one with a lime green dinosaur print on it and matching stickers from Next, years ago now.
Paint is the easiest colour to pick, you start with what you can't change, usually carpet and furniture then go from there, soft furnishings next (bedding, curtains) and then paint. I did an interior design course years and years ago but this stuck with me.
I shared a room as a child so never got what I wanted. 