I agree with Phil and Paul 👍. I think this is kind of an "in-joke", with a touch of irony added, considering that Bella is a vampire (or will soon be one - depending on which film you are watching) - which is a bit crazy in itself. But (ironically), even more so for Jacob, who has the ability to transform himself into a giant wolf (werewolf?). Jacob often makes jokes of this kind with Bella, linked to their respective 'alter egos'.

That would be the usual Spanish word for "crazy", in the feminine singular (in the masculine singular, "loco"). Spanish is the most frequently heard foreign language in the USA, so many Spanish words are in common use, especially in California, large East coast cities such as New York and Miami, and near the Mexican border.

Maybe local slang for local

Hi friends, what's the meaning of 'loca'? I saw it in a movie where a boy named Jacob, who is a Native American, is greeting a girl name Bella: "Bella! Where have you been, loca? " Thanks! I completely agree with Phil. Many Spanish-speaking people from México, Puerto Rico and other parts of Central America came to America to settle (live) there. The name 'Bella' means beautiful in Spanish and the word loco/a means crazy. For some reason he has chosen to give her the nick-name 'loca', my guess he says it on both a colloquial and affectionate kind of way! 😀 I hope this helps you 😀

Self-correction: says it IN both a colloquial and affectionate way.