so obviously you all know how much Lewis hated Susan. I mean, he dedicates an entire page of The Last Battle to having her family and friends slag her off. Lewis goes out of his way to break down her character. why, you ask? so did many of his fans at the time. he received countless letters demanding an answer. the one he gave was that Susan was to be a cautionary tale to always stick with your family and not fall to vanity.
HA! proclaimed most of the literary community and critics. Susan's fate was most likely due to Lewis' vendetta against female sexuality, as the vast majority of the criticisms of her were targeted at traditionally feminine vices. also, she is supposed to represent a loss of faith - Susan, the sensible, logical, reasonable child, who always tried to take responsibility, is of course the one to stop blindly believing in a talking lion and a world no-one knows exists. (I personally think there's far more to it than that, especially if you consider the psychological trauma of being torn out of a world to repeat puberty, only to be taken back and torn away again.*)
so that's the background. and here's what the film did with it.
at the beginning, we see Susan being harassed by a young boy. he approaches her and starts talking to her about how he's seen her during school, despite the fact that she doesn't make eye contact, continues to read her magazine, and gives short answers. she is clearly uncomfortable with this unwanted attention, and even goes so far as to give a fake name. why is this important? because it shows that her attractiveness is already a burden to her, because it shows male attention as invasive. because it shows that her sexuality is causing her problems. this is a complete subversion of the original canon, wherein one of Lewis' pet plot points was female sexuality causing problems for others, namely poor male protagonists.** not only that, but it's a defence of Susan - she doesn't mean to be this pretty, and she shouldn't be blamed for it.
movie: 1, Lewis: 0
as the movie continues, Susan is a total badass - she actually takes part in the battles, talks sensibly to everyone, doesn't take any shit, and in general is just a hbic.
movie: 246, Lewis: 0
oh and that conversation with Lucy, when Susan haltingly asks why she didn't see Aslan, Lucy replies that "maybe you didn't want to see him." ouch. that one hit me right in the Susan-loss-of-faith feels.
movie: 49386, Lewis: 0
then, as the children's journey continues in Narnia, we get a Susan/Caspian romance subplot. let me say that again - SUSAN GETS A ROMANCE SUBPLOT. (the only romance subplot we get in the books is Caspian randomly marrying some girl he just met, who doesn't ever have a name btw, simply bc he's dazzled by her beauty***.) but in the PC film we get to see Susan take charge of her sexuality. she has male attention that she enjoys, as she grows into an understanding of her budding feelings for Caspian. not only that, but it's clear that Caspian doesn't just like Susan's looks, but admires her as a queen and a warrior. (plus their banter is just so precious - after Caspian returns her horn Susan says "why don't you keep it? you might need to call me again.." al;sdkfjasd Susan you card!) and this all culminates in Susan kissing Caspian, passionately and right in front of Aslan and a crowd of Telmarines. I just !!!!! holy sexual agency, Batman!
movie: 54830346, Lewis: rolls in his grave so much he burrows to China
of course, the film is otherwise hugely flawed (who the hell decided that endless Telmarine politics was a good idea?!), but in regards to Susan it provides us with what the books never did - it shows her as a person, flawed but fantastic, who totally shouldn't be blamed for her sexuality.
* the film actually comments on this too! and through Susan! in the tube station she advises her siblings to accept the fact that "this is our home", and when they are returned to Narnia she bemoans the fact that "I had just got used to living in England". A++ character depth and also Susan defence.
** see: Jadis and Edmund, but mostly The Lady of the Green Kirtle and Rillian. (oh and there's that plothole of TLotGK needing Rillian to rule with her, when she had an entire army and was ready to invade Narnia and was clearly powerful enough to accomplish this on her own. so why this ridiculous kidnap of a male? because female sexuality is daangerous, kids!)
*** don't even get me started on the Dawn Treader film, and how it not only gave her a name but also agency to fulfill the purpose she was written for. actually just don't get me started on the DT film in general because it is my favourite and I will go on about it forever.