User blog comment:SayuriDarling/The House of Hades Official Discussion/@comment-5927468-20131013202800/@comment-23784532-20131016184929

That is true about her immortality, but on her island she is immortal, off of that island I think she would be as mortal as a pumpkin. If Leo stayed on the island with her, or removed her from the island, then they would be equal. Percy made the gods agree to free her and they did. They did not agree to remove her from her island. And Calypso wouldn't try to go with him. For all we know and she knows she could be able to get off of the island but she has to try.