The high-profile couple split at the beginning of the summer (09), but friends claim Hilton is the subject of recent Twitter.com posts from Reinhardt, in which he coos about his love life.
A source tells UsMagazine.com, "They are definitely happy again.
The couple started dating at the beginning of 2009 after Hilton split from Good Charlotte rocker Benji Madden.
Reinhardt recently posted a 'tweet' on Twitter.com, stating, "What an amazing weekend with my beautiful girlfriend. I love her so much!.
In a spring interview, Hilton declared she'd marry Reinhardt, explaining, "I'm really in love and really happy.".