|it differs quite a bit from what you wrote, but I can't help thinking it's Can't Lose You. Yooi takes a job acting as a double for a rich girl who looks identical. She falls in love with the other girl's fiance. Major spoilers:
Spoiler (mouse over to view)
Yooi and the rich girl are actually twins. Yooi gives her twin her blood after an accident. A fortune teller predicted that one of the daughters, signs indicating Yooi, would be strong but would end up killing her father (or maybe it was a grandfather? been a few years, I'm fuzzy) so Yooi and the fiance are in love, he's going to take her far away to be safe from the father, but she leaves him for his own good yadda yadda. it works out for the two in the end though.