You got him - Raphael Boyfriend Scenario

You weren't just a girl. Not human and not even a mutant that was known by any others. You were a demon but also a werewolf. A new spezies in the world. But you weren't an experiment by the Kraang. Both of your parents were werewolfs. But after you were born something happened that you had to deal with this new demonic feeling in your soul. And living like this in a world full of humans that needed to get a lection was not easy. You had a short temper and pretty known around your area and in the school. So it wasn't unexpected that the turtles and even shredder heard something about your powers. And Raphael started to be interested after somekind of accident which he saw in action.

That's how your story as chimera being in love with a mutant started.