The past

A girl born with a mark on her face,was taken in by death ( Lady Death), anyway she helps the world and saves it, on top of that, she's starting to fall for 2 guy's who both love her,and they are in a relationship anyway she travels accidentally to another world and finds out that the mark belongs to a dooms day bringer and she has to marry him or both worlds will be destroyed, can they save her?, what is so special about her?,find out.