Aquamarine going to the town specifically to look for love. Her first experience witnessing it was watching Claire's parents in the sea nearby. And she said she went there again, so it makes sense that this would be the first place she goes.
Why didn't any of the friendly things Claire and Hailey did for Aquamarine count? Because, while they may have been having fun, they did have something of a selfish motive - getting the wish to allow Hailey to stay in town. But at the point they jump in to save Aqua, Hailey has already decided she won't use the wish to force her mother to stay - so it was a truly selfless action that could only have been done out of love.
Aqua is incredibly confident and sure of things. Well she does often have starfish attached to her ears giving her endless compliments - so she's bound to have lots of self-esteem from it.
It also helps that the starfish don’t lie; so even though they’re suck-ups, the compliments they give are completely genuine. So Aquamarine is confident, but (unlike Cecilia) not to a delusional, bratty degree because she knows what her strengths are.
For helping Aquamarine escape from the water tower, it's implied that Leonard uses his wish to gain the favor of a woman he's been interested in. Seemingly without considering her say in the matter—and in a movie that's supposed to be about how you can't expect or force someone to love you in a very short time frame. Yet he's never treated as being in the wrong for doing this, and the negative connotations are never brought up.
Well we don't know specifically what his wish was for. Aquamarine says the wishes can't violate the laws of nature, so maybe there are limitations on interfering with free will - so maybe if Leonard did wish for that, Aqua would tell him it was impossible or advise him not to. Or maybe he just wished for the confidence to be able to talk to her himself.
It's likely you can't just wish for someone to fall in love with you - since couldn't Aqua manipulate things to get the girls to use their wish for that?
