Well Edenia doesn't have Brazilian, Hispanic/Latin-American, or Spanish ethnicities nor does it have Middle Eastern, so it's safe to say Jade is none of these.
As far as appearance goes, she is a darker skinned, dark-haired woman. To me she does not strike me as latina (being half Puerto Rican myself), but rather Egyptian (as far as model goes), her very outfit has an arabian feel to it. Looks wise she could pass for latina, but to me she's more Middle Eastern in terms of her outfit, appearance, and the fact most fantasy tropes do have a desert/arabian tribe or culture while few if any have South American influences.
Lol yea better keep it above the belt that would be gross. Lol i want to see a hispanic girl. Lol u know mk not really making black ppl, lol only one black guy that's a real shame but I think cyrax is black? Lol this is so funny.. One of the reasons my friend doesn't like mk is because too many white ppl hahahaha
White: Johnny Cage, Sonya, Kobra, Kabal, Kira (not *that* many)
Black: Jax, Kai, Darrius, Tanya, Cyrax (I know Darrius and Tanya are technically in Outworld but they are black in complexion)
Asian: Liu Kang, Kung Lao, Li Mei, Bo Rai Cho
Mixed: Kenshi (Eurasian), Kano (Eurasian)
Native American: Nightwolf
Ambiguous: Jade, Kitana (though all are technically Edenian, Kitana has been portrayed by hispanic and non-hispanic white actresses, in Deadly Alliance onward she does have a hispanic/meditteranean flair to her appearance while Jade is passable for being middle eastern or even an african/arab mixed woman)
The rest really don't have an apparent ethnicity but rather different shades or complexions (or not even human or humanoid). But there's plenty of whites AND blacks in the MK Universe lol, don't see why your friend would say that.