I also don't think that they really ever broke up. I think they both need each other. I don't think Heidi can make any decisions without Spency. If they had really broken up, I bet Heidi would have tried to get back with her family. She just doesn't strike me as someone who could be alone. And we haven't heard anything about her trying to reunite with her family.
From when they first started dating on 'the Hills' Heidi seemed to think that Spencer was so together and was going to do great things for her career - she probably still believes that - poor girl.