Or determination, once she decides to do something, she does it!

Yep, she is pretty stubborn.

With Eric it's an obsession but she's more determined than anything else.

Obsession is fun!

Impulsiveness and determination basically go hand in hand rgarding her characterization which makes her incredibly unique compared to other princesses that are either restrictively reckless & thoughtless OR too calculative and passive.

These are fantastic questions :)

She is pretty stubborn and never gives up on her dreams.

I think she's the most naive princess.

^ I don't think she is naive. Being naive is, in other words, being blissfully unaware of danger in the world through lack of experience and/or lack of judgment. A naive person is basically a person of innocence (a good example to use here is Snow White). I think Ariel completely knows and is completely aware of what she's doing, for the most part anyway, and I wouldn't really call her "innocent"