for me, it is more logical that veranderen should be a reflextive verb.
Yes, but it's not about logic, as languages aren't the most logical systems in existence. :)
"Zij moet zich veranderen" Haar gedrag, gewoontes etc.
Why isn't it "Zij moet haar omkleden"?
Zij moet zich verkleden. Omkleden more often means to clothe yourself, maybe like when you come out of the shower!! Please include this word, especially since we Dutchies use it more often than omkleden.
"She has to change" is too ambiguous. "She has to get changed" would make it clear that "zich omkleden" was required, not "veranderen"
She has to change what? Her clothes, her attitude, her job, her...? This is an ambiguous sentence.