Singers Katy Perry and Travis McCoy have ended their relationship, a source tells us.

The "I Kissed a Girl" singer, 24, and the Gym Class Heroes frontman, 27, vacationed together in Mexico over the holidays, but they split shortly before the New Year, says a source.

"It's a hardship, but she's regrouping," a source told Celebuzz, which first reported the split.

McCoy took to his FriendsOrEnemies.com blog on Dec. 31, where he posted lyrics to hip-hop group Main Source's breakup song "Looking at the Front Door."

The song includes the lines: "We fight every night, now that's not kosher/I reminisce with bliss of when we was closer/And wake up to be greeted by an argument again/You act like you're ten."

He followed the lyrical post with another loaded message, declaring his devotion to his laptop: "My Laptop is my new b–. LOYAL. LISTENS. and NEVER LET'S ME DOWN."

The same day, Perry performed at the Gridlock New Year's Eve party on the Paramount lot. "She hung out with her friends all night. She was in a great mood," says a partygoer. "Nothing seemed out of the ordinary."

After more than a year of friendship and casual dating, the musicians got serious right before both hit the road for last summer's Vans Warped tour. McCoy bought Perry a "promise ring," he told PEOPLE in June, while he wore a silver band with the word "Katy" on it.

A rep for Perry, a Grammy nominee who kicks off a tour Jan. 23 in Seattle, had no comment on the singer's personal life. McCoy's rep could not be reached for comment.