Demi Lovato and boyfriend Wilmer Valderrama hit the rides at the Knott's Berry Farm at Buena Park, California along with friends for her post-birthday celebration over the weekend.

E! News reported that the couple could not get their hands off each other, and were even locking hands during thrilling rides.

The witness told the entertainment news site, "They made a lovely couple. They indeed looked very happy."

The website also talked to another witness who claimed that Demi Lovato and boyfriend Wilmer Valderrama were all over each other and at one point were "making out" after dinner at one of the restaurants inside the theme park.

Demi Lovato graces the September 2015 cover of Cosmopolitan and in the accompanying interview, she gushed about boyfriend Wilmer Valderrama and how he helped her get off drugs.

She said, "We started dating when I turned 18 ... Right after that, I went to rehab. People told him, 'You should probably leave. She's on a spiral, and you're going to be sucked down with it.' But he was like, 'I'm not leaving. This is somebody I really care about.' We relate on a lot of levels. I've seen a lot of shit. Shit people don't know about. He's seen a lot of stuff too."​

But their relationship wasn't made of fairy tale romance, and that's why it endured.

Demi Lovato said of boyfriend Wilmer Valderrama, "The only times we ever broke up were when I was relapsing, whether it was drugs or in a bad place and rebelling against everybody, not just him."

"The times we'd broken up, I had already gone to that place of, 'Yeah, this is what's happening.' I didn't realize it at the time, but I just wanted to sabotage everything around me so that I could sabotage myself," the "Heart Attack" singer added.