To me it sounds like you need to explore the villain a bit more.
Why does he want the jewels? What does he have to gain by taking over the world? He's going to need acquaintances, both people who are working for him and who are working against him. Why are his allies working for him in the first place? Has he offered them a reward? Are they genuinely his friends? Do they all believe they are doing the right thing? Asking questions is always a great way to figure out where the plot goes. You can do the same thing for your main character; who are her friends? What are her motivations, beyond just saving her family? Is there anything she wants that is unrelated to saving the world?
I personally think betrayal's a fun theme to write about. Maybe the boy who's helping her is temporarily persuaded to assist the villain. Maybe he doesn't realise what he's doing when he does it. This could generate all kinds of conflict. Or maybe they meet someone else who pretends to be their friend, but is actually spying for the villain.
Just some ideas.
Hope they help!
That might be interesting. 