Oh yeah she would! That could be a fun game casting that movie. There are so many great and interesting characters in it. It's absolutely one of my favourite books ever. I have most of your mum's books... there are only a couple of the very early ones that I don't have but I do keep an eye out for them in second hand book stores but as I'm in NZ I don't hold out much hope of stumbling across them... I keep looking though!
How about Benedict Cumberbatch as Philip Dapifer?