There are many reasons why I don’t buy the cynical interpretation that Ariel gives away her identity for a man.
One of them starts in the next paragraph. Another one can be read here.
This screencap comes from her introductory scene. She’s searching through a shipwreck for human artifacts–which is her passion–when suddenly she’s attacked by a shark.
While fleeing, she accidentally drops her bag full of artifacts right in the shark’s path. Without hesitating, she chooses her passion over her safety, risking her life for a dinglehopper.
The girl is an anthropologist who studies humans. That’s her passion, that’s how she spends her time…that’s her identity.
Sure, Eric is the catalyst that leads Ariel to changing her species and leaving her family–he certainly intensifies her feelings–but they’re feelings she already has, and they dictate most of her life.
If Ariel had the chance to become a human before she met Eric, everything that we know about her suggests that she probably would.