If A loves B truely and cant live without her, dying is certainly not an option. There is no way a person can be loved but to let they self be loved. you must have heard bout it. right ?? therefore he should let himself be loved. do the act dont sit and wait for her to come and love you this is not going to happen. If you love her just go for it. may be she had relationship with someone else before she was with A. but A was ready to then accept her irrespective for what there was, like it was a new start.so let there be a new start again. love will change things. you gotta make her realize what she is doing is not right. just go to her explain things and may be you could have a new start again. and A has gotto be true to him self has he always been sincere to B right form the start. put your self in the situation. Its heard to find true love and 90% of people are cheated its up to them to give up or get back. so go try hard. all the best.