there has been no emma frost in films yet.
the version in wolverine origins was nothing at all like the character
and the version in first class, while closer, is still a shell of a woman the character could be.
i think either natalie dormer, charlize theron, or robin wright would be perfect for emma. ideally, a combination of all three haha.
the key is that she actually needs to be shown as a deep character. the tricky thing with emma is that 90% of her character is behind a lot of layers. on the surface, she’s seemingly a cliche bitch. but there is so much behind her as to why she is this way, that within the limits of a single film, it would never do her justice to be any less than a second billings character. she needs to have black widow level prominence to really be able to see past all her defenses to where her true personality and motivations are. there are a lot of characters in the xmen who just right off the bat, are very captivating. you can understand a lot about them within one issue with them (like wolverine, storm, beast, magneto, mystique etc). emma is not that character. she is fundamentally written as not that character. her personality and characterization is all about the walls she builds. and if we can’t delve into that, there won’t be an adaptation she deserves.