Hitch - I don't understand the ending...

[ThomasRichard]

...and it's irritating me. Why is Sarah so horrible to Alex when he goes to her apartment? Why is she smiling behind the door?

Does this help? From Wikipedia...

Hitch then tries to salvage Albert and Allegra's relationship. He confronts Allegra, telling her that he doesn't really do anything significant besides giving his clients confidence and allowing them to get the attention of the women, and that most of his customers, particularly Albert, really were successful just being themselves. Allegra reconciles with Albert. The film ends with Albert and Allegra getting married as well as Hitch and Sara resuming their relationship.

Thanks. I know that bit, it's just the scene with Hitch talking to Sara at her apartment, which ends with him jumping onto her car that I don't understand.