My sister what’s to be called Tia

So, I am concerned my sister is culturally appropriating and doesn’t realize it. She and I are like crazy pale, and she wants to be called Tia for my little baby. The word itself is a beautiful Hispanic word meaning Aunt, but would this come across as strange to people coming from one white Lady to a more then likely paler baby? My husband is Spanish (edit: as in FROM Spain, I wasn’t just using a generalization) and has just rolled his eyes at it. Has anyone else called family members names from other cultures other then there own? Or should I have a talk with her?