What If Eric Married Vanessa? (TLM- Never let me go)

Hans Christian Andersons classic tale meets Disney
The little mermaid save the prince, but he was found on sure by a woman who lived nearby so he thought she was the one who saved him. the mermaid made the deal with the sea witch and became human for the prince but by this time he had already made plans to marry the girl he met on the beach. Thus leaving the little mermaid to go back to the ocean and fade away.
I've made this as if eric met ariel and fell for her but had already agreed to marry vanessa so she goes back to the ocean and he sees her and follows her then sees her die.
the end scene is meant to be her spirit being set free