"She is changing her character."
Translation:Sie wechselt ihren Charakter.
I'd prefer that, actually.
The meaning of this sentence doesn't seem clear to me; if she "changes her character" = "she chooses to use a wizard instead of a warrior" in a computer game, both work, but maybe "wechseln" works a bit better. I think it's only recently that the word "Charakter" has been in use for "fictional persons" in German as well.
If "her character is changing" = "she's often so angry these days", then "She is changing her character" doesn't sound like good English, right? But it seems the more likely meaning they intended, doesn't it? In this context, you'd have to use "ändern", not "wechseln".
In short, "wechseln" = "to exchange one thing for another", while "ändern" = "to change", possibly just "to rearrange".
Yes, I tried the same translation: "Sie ändert ihren Charakter" but that was not accepted (copy and paste). "Ändern" is also a possible translation for "to change" (dict.leo) and it is more likely that she is changing her character, than that she turned into another character = "wechseln". (reported).