Dark Horse isn't trap. It isn't urban. It's kind of an innovative sound that isn't really comparative to anything. Sure, you can say it's pop, but pop is a really broad umbrella that pretty much every song that's slightly popular could fall in to. It's got a really hyphey beat. If I had to give it a genre, I would say it's hyphe-hop, but that's not a genre anyway. Another song that I would put in this 'hyphe-hop' genre would be 'Pop the Glock' by Uffie. It's clearly influenced by electronic music but it's not uptempo and dancey enough to be classified EDM. But it's trippy.
Everyone accepts that Dark Horse is trap. It's not even considered pop. Wikipedia has it labelled as trap and hip-hop, which I know, "anyone can edit that!!!", but it's been like this since 2013 and Wiki are very strict about their genre classifications. If it's not accurate it cannot be accepted. I'm sure if some ATRL member tried to edit it, Wiki people would change it back.
Lyrically Dark Horse might not be trap or hip hop but musically (i.e. the beat) it definitely is. I listen to that kind of music all the time, I recognise it from a mile off.
But congrats to her!