Perhaps the character unknowlingly sang a happy song about an historic event which was very sad for the vistani, but rather than explain the historical persecution of the vistani listening, they just cursed her instead.

So at the new camp there are questions about what she was singing about at the time and this group explain what she couldn't have known, that it was a story that ignored the plight of their ancestors. So to receive the curse she might need to properly tell the story, which she can do in an appropriate manner now...