Sheikh Yasir Qadhi made clear on his call in show in 2020 that the 3 schools: Hanifa, Malik, Shafi forbid hair being seen. One exception is the Hanbaly school. It allows the woman to make that decision. However she is not obliged to show her hair.
The Sheikh did add that in some cases the hair can be seen once the contract has been signed. However on this point there is controversy.
Question: Is it permissible for a female to display her hair infront of her fiance before the Niqah?
Answer: If a man has seen enough of his fiancée, within the limits set by Islam, to enable him to decide whether to go ahead with the marriage or not, then it is not permissible for her to uncover any part of her body in front of him until after the nikaah. (See also question #2246 and #2572). And Allaah knows best.