I think it’s her mouth, which seems about three sizes too large for her face. And of course there are all those freaky voices she uses when rapping. I’m sure she’d consider “frightening” a compliment.
I’d use a much different adjective to describe her body, which is the sort of post-modern bodacious Varga girl spectacle that makes men say “DAAAYUM!” and bite their fists with mounting frustration.
I don’t have a handy adjective for her music, because thus far I know her only through her work on other people’s records.