Speaking to E! Online, the heiress dismissed rumours that she is already engaged to Reinhardt, but admitted that the couple are "best friends".
"It’s not like we just met. We’ve known each other over the past year. I was in a relationship before and we reconnected. I’m really in love and really happy," she is quoted as saying.
When asked about the future, she joked: "He's going to be my husband."
Hilton started dating the baseball player following her split from Benji Madden earlier this year. Reinhardt, who has also appeared on MTV's The Hills, was previously linked to co-star Lauren Conrad and actress Amanda Bynes.