@Jasmine: She most likely would have been young or possibly adult with a youthful appearance. I’ve actually seen some actors and actresses in movies that look younger than they really are. But that’s kind of beside the point. So, it’s possible the White Witch may have been an adult with youthful appearance. 

Normally, in Western society, we judge who is a child and who is an adult by legal age. I reached the age of adulthood, in 1969, at a time when the age of majority was 21, enabling me to vote, marry without asking my parents or be otherwise treated as an adult. This age was reduced to the age of 18 years about when my eldest child was born in 1972. You say that some actors & actresses in movies look younger than they really are, a very good point, when the ability to disguise age is part of their professional work, and there are also people, I agree, who work very hard at staying younger than their actual age. In her only other book appearance in the Narnia Chronicles, Polly says of Susan:

"Grown-up, indeed," said the Lady Polly. "I wish she would grow up. She wasted all her school time wanting to be the age she is now, and she'll waste all the rest of her life trying to stay that age. Her whole idea is to race on to the silliest time of one's life as quick as she can and then stop there as long as she can." 

We never find out what sort of actual work Susan would likely be doing, once she left school. C.S.Lewis did write to someone about Susan that though she was proud and vain in The Last Battle, she would have time to change in her own way, when she was the only one of the Pevensies, who remained alive. 

Whether for career or social reasons or whether it is a natural lifestyle choice, many do try to keep looking as young as they can, until well past middle age, which is roughly in the 50's age bracket, when certain physiological changes can & do take place, along with that particular milestone. One or two decades later, retiring age is the next milestone, at the traditional three score & ten, though some still can work well into their eighties & nineties. But by that time health can also go downhill fast. It is cruel of thoughtless people to call elderly women "old hags", or "old witches", either, in my opinion, when elderly women are often too fragile to be anything of the sort.

Jadis, I think, goes into this category, of staying at the same age for the rest of her life, sort of "mutton dressed up as lamb", as the likes of Aunt Letty would say rather witheringly. Usually, it is done with paint of one kind or the other, whether as cosmetics or in the case of statues, actual paint. But it seems that Jadis was skilled with magic. Therefore, I don't think Jadis' actual age is relevant to the plot when Jadis wants to stay at the same age forever, anyway. 

This link is to some video of the actor I most like playing the WW, who is showing WW as mature but young.

She is in fact the Artistic Director of the Logos Theatre. The videos are from their current run at the theatre in the Museum of the Bible, Washington DC.

I had always pictured Jadis to have black hair. Not because of the illustrations or first film adaptations of her. I just always saw her with thick wavy or curly black hair. Probably why I was not bothered when I heard Chari XCX was up for the role since she looks exactly how I imagine Jadis would look.

She is the right age too as how I imagined her as well, which is 25-35.

As I've said before I just struggle to picture Charli XCX in the role. For one, I'm nervous in regards to her experience and calibre as an actress. I feel like this isn't role you risk on a fresh face. Also, in terms of her physicality I can't imagine her coming across that imposing.

For one, she's only 5′ 3″, so I struggle to see how she could embody the "part-Giant" aspect. Even though Tilda Swinton was given those high boots to make her seem even taller, she's still 5′ 10″.

I was hoping they'd go down the route of Elizabeth Debicki, who not only has the experience and the acting skills, but she's also 6'3″ and only a couple years older than Charli at 34 years old, so still fits within the age parameters you imagined @daughterofthestar 

Posted by: @daughterofthestar

Probably why I was not bothered when I heard Chari XCX was up for the role since she looks exactly how I imagine Jadis would look.

Thing is, we don't know that Charli XCX is up for that particular role. We only know that she's been named as being considered for "a" role, with no official word as to what it is. Of all the casting rumours so far, the only one that has paired a star with a specific character, right from the first report, is the rumour about Meryl Streep playing Aslan. All the rest came as just hints that this person was being approached, and other media outlets have added speculations as to which role they may be offered.

I also agree that Charli XCX isn't tall enough to make an obvious choice for Jadis, although there may be ways they can get around that with clever filming tricks, if she is otherwise what they want for the role. Given that we're getting more and more evidence that this version of MN will not follow the book closely, though, I don't think we can be too sure about what any of the roles will be!

Yeah exactly @courtenay, again while I'm not a fan of possibility of Charli as Jadis, I'm certainly not against her being in the film as another role, whether that be Digory's mother, Helen or even Sarah.

@rilianix 

Of course I can understand where you're coming from. First thing I want to get across from my perspective is the essence Charli gives off when it comes to Hollywood's determination to casting an actor today (with what I've experienced as an actress myself), not so much an actor's ability. Charli has that diabolical and witchy way about her. She has the look of a villain and can portray a mean character by her looks alone. The talent comes later with direction once on the film set. 

As for her height there have always been height enhancements done in films like with what you said they used high boots for Tilda Swinton when she played the WW. There is also CGI and trickery of camera angles.

@Courtenay

Of course and there's also the possibility that she could be in talks of a different role. I never said she was being cast as Jadis just that she was up for the role seeing as shes already got credit on IMDB for the Narnia project, but not listed a character, it does seem she has snagged something for the film.

Also I want to apologize for getting this topic somewhat off track.