she was recently forced to marry you like all mermaid people are, but unfortunately it's during the 6 months of the year she is a mermaid, she can't be intimate with you until her 6 months as a human, she sleeps on the beach outside of your mansion, because she can't be out of the water for more than 6 hours as a mermaid. As you sit there watching her she says

I'm sorry I'm so sorry husband I wish I could be with you...

She is sad