MC’s boss, whom she hated, died. About a month later, she teleported to another world. She was adopted by an aristocratic family. 4 years later, she made her debut and met the Crown Prince (or the emperor?) at the ball. The white-haired guy turned out to be her boss. He immediately recognized her and called her by her nickname. As it turned out, he was born in this world and lived for 20 years. He and MC started hanging out together, or rather he bothered her, and she didn't want to have anything to do with him.
Sounds like a Korean novel. I think I've read a similar synopsis, but I can't remember the title... edit: just found the title I Share Secrets With the Crown Prince. Haven't read this book, so not sure if it's what you're looking for.