BEIJING — As Huawei’s finance chief and daughter of its founder, Meng Wanzhou has been a polished, professional face for a huge technology firm that long was opaque to the outside world.

Ms. Meng, the eldest daughter of Ren Zhengfei, the leader of the telecom equipment maker, has appeared before reporters to announce the company’s financial results. She has spoken at company events in New York; Cancún, Mexico; and beyond. She helped inaugurate centers in Britain, a key market for the Chinese giant’s expansion into the Western world.

She also sat on the board of a Huawei partner company in Hong Kong called Skycom Tech that Canadian authorities now say did business in Iran. And through that position and her job at Huawei, Ms. Meng may have personally been involved in tricking financial institutions into making transactions that violated United States sanctions against Iran, they said.

That has thrust Ms. Meng, 46, into the center of what promises to be a complex diplomatic tussle between the United States and China. She was arrested Dec. 1 in Vancouver, Canada, while changing flights, at the request of the American government, which is seeking to extradite her. The action escalated what had already been a roller-coaster year of economic conflict between the two powers, ahead of tricky negotiations to end a brutal trade war.