There was just a news article about US corporations hiring North Koreans for remote work unintentionally, and the north Koreans then did a sabotage and stole secrets... Strikes me as HR is freaking out across the board and they were looking to confirm you aren't actually based in a foreign country. It is very easy to hide where you are(phone numbers can be forwarded, addresses can be false). If it's a 1 time thing, not racism, if they consistently single her out, is there anyone else of her race being singled out? Did HR maybe get a derogatory report from someone that doesn't like her and they wanted to see if she was sober? That's happened to me.
They are waiting for a tangible response, and building.