They are getting downvoted but may be genuine. I as a European person also didn't immediately see her as black, just based on appearance. Closer to North African / Arab / Middle Eastern. Given that Eritrea is right next to the Arabian peninsula, it's not surprising.

It wasn't necessarily meant as an insult. Perhaps in America it's clear she's black, in countries with more North African and Middle Eastern immigration, it may not be.

The geographic distance from Eritrea to West Africa is the same as to Denmark (like 5000 km) and the terrain isn't easy to traverse. If someone imagines all black people "must" look the typical West African way (Ghana, Ivory Coast etc), they may be legit confused when seeing someone from the other side of the continent. The reason that both are considered black is social.

Edit: for example, when seeing her photo she reminded me of the Syrian-Hungarian reporter Hesna Al Ghaoui: https://hesna.hu/gallery#media So precisely what skin tone qualifies you as black is hard to say. Somewhere between Al Ghaoui and Gebru I guess: https://c.files.bbci.co.uk/B817/production/_115872174_gettyi...