I think that she is saying that she is the only one who would sacrifice herself completely for her lover "i'm the only one who'll walk across the fire for you" and put everything that she has into the relationship and that no matter whoever comes into her life no other woman will love her like she does.
I think that she is saying that she is the only one who would sacrifice herself completely for her lover "i'm the only one who'll walk across the fire for you" and put everything that she has into the relationship and that no matter whoever comes into her life no other woman will love her like she does.