I don't think Mirte is very pretty, but she does have an aesthetic that's compelling.
Besides, if Karlie Kloss and Lindsey Wixson landed beauty campaigns, I don't see why people are surprised someone like Mirte can. She may not be conventionally pretty like Barbara Palvin, but she doesn't look very unconventional either. Lara Stone, who's no conventional beauty either, was considered acceptable for beauty campaigns. Ditto with Muse.
Bottomline: beauty campaigns stopped being about casting the most classically beautiful girl a long while ago.