Can't speak for everyone, but she won me over in the first episode.
When she eats the Glowey-O, and sees that she's glowing, what does she do? Does she scream? Is she even all that surprised? No. She says "Oh, cool!" and puts on that perfect smile of hers.
Contrast this with the characters you normally see. They see that magic is real, or that a superhero's showed up, or they're in a spaceship. What do they say? Maybe they scream. Or they'll take ten minutes just to comprehend the new change. Or they'll react with hostility, and try to escape or attack something.
If Luan were suddenly beamed up into a spaceship, she'd just roll with it! She doesn't care whether or not things really make sense, let alone whether or not she actually expected them. I interpret that as an incredible confidence in herself and her ability to handle any surprise or setback that comes her way. That's a skill I've been working on for years.
Not to mention that some of her jokes would actually require a certain amount of wit - and, again, confidence - to pull off. Again, she won me over in the first episode. When she stops glowing, she says "I thought I was staying in tonight, but I guess I'm going out!" Now, what does that require? She has to draw the connection between "I'm not glowing anymore" and "I'm going out," and then connect the two different meanings of the latter. Then she has to find a sentence to fit the phrase in. That takes some respectable mental power. Sure, she's probably doing it subconsciously - but that in turn requires confidence in oneself.
That's why I love Luan.