Al is new in town after moving here from the big city [whichever big city makes sense]. Her father is an oil field inspector, so he's gone from home a lot, and her mother is a stay-at-home-mom. Al loves the city but her parents decided to move to a small town instead. They're not filthy rich but they're pretty wealthy so she never really had to worry about money at all.
Al is pretty, adventurous and wild. She loves going exploring, investigating mysteries and making up crazy theories about whatever thing has caught her attention this time. When she arrived in this town, it didn't take her long to make friends and become pretty popular. If you're new in town, you either become an outsider or an interesting new friend to everyone and her general openness have caused Al to become the second one, without a doubt.
Her motto in life is "I'll try everything once". Or maybe it's "No risk, no fun". Or maybe "What doesn't kill you makes you stronger". Or "I'll eat any pizza, as long as it doesn't have broccoli".
Sometimes, her little brother Benny can be a bit of a nuisance and when possible, Al tries to shake him and spend time with kids her own age, but she loves the little bugger and always takes care of him. He looks up to her and thinks she's the coolest person in the world (which she wouldn't necessarily disagree with).
Al's dad is rarely home but when he is, he showers her and Benny with gifts and affection, always trying to be the cool parent. Her mom is more strict and serious, though she can still be fun when she wants to.
The two of them have some marital problems and tend to fight a lot but they try to hide it from their kids, so Benny is completely unaware of it and Al only has a vague idea.