Jason Todd

WARNING: This idea is mine and based on the Batman game.

You are Poison Ivy's daughter, but unfortunately she died saving the city from Scarecrow's venom. Unlike your mother, you are a heroine alongside Batman. Before all this happened, you were dating Jason Todd, but one day he was kidnapped and Batman did nothing, unfortunately. You were very sad since you were engaged to him; you and the Wayne family thought he was dead. Then, after a few years, you moved on, but you always kept him in your heart and went to the place where you kissed for the first time.
Nowadays, you're dating Dick, you guys had a new villain in Arkham Knight, Batman found out who it was... it was Jason. He hated Bruce for leaving him with a huge "J" on his cheek that the Joker had given him before. Then Jason disappeared, Bruce didn't tell you anything about it. But now you have a new vigilante, Red Hood, who is Jason. You went after him.