In (500) days of summer, why is summer engaged when she didnt believe in love?

when they were on the bench (for the last time), she admitted that tom was right. she realised through him, that love is real, and although they broke up, she believed it was true when the other guy came into her life.

btw this is like seriously one of my fav movies of all times. tom is so hot :)

She just found the right person. Simple as that. Women, eh?! :-)

From a dramatic point of view the engagement is there as a 'kick a man when he's down' tactic.

I've never seen the movie it sounds pretty good though. All I know is that Vulcan's they don't believe in emotions period and they still get married. (like Spock's dad who is a Vulcan married Spock's human mother because he was the embassidor of Vulcan and it was logical to marry her to learn about human ways and culture) Yeah. That's all I got.