Ginny is a very skilled witch evidenced by how JKR describes her in the book. At age 6 she started taking her brothers' brooms out for flying lessons. By her second year, she could conjure a singing Get Well Card for Harry. Somewhere between her third and fourth years, she learned the Bat-bogey hex, striking fear into Fred and George. At least in the movie, she seemed to have little trouble conjuring a patronus.
What, you've never heard of pre-ordering tickets?
and coffee? :o)
(Enjoy the film, Joe!)