It has been four years since Melody has chosen to stay on land. Does she regret it? Sometimes. She did it to make her family happy.
The major change in her life since then is she is madly in love with Alex. She only barely knew him four years ago but now she spends every second she can with him.
Her parents are glad they found the one. They except him but they know the fact that they are loosing her to him as well. She is eventually going to want to go back to the sea to be with him.
Ariel knew it the day melody told her about him. She knew melody wasn't meant to be in this world just like she wasn't meant to be in that one. She knows what it is like living in a world you don't belong in.
Ariel use to be so interested in every human object she found, ever human event she could see. Melody was always drawn to the ocean, even before she could talk or walk. At first she thought it was because it was part of who she is. Child born of land and sea. Now she realizes that isn't that case. It isn't part of who she is, it's fully of who she is.
Now it is about spending every moment with her as if it were her last.