09/04/2008 AT 10:20 AM EDT
Listen up, fellas. When it comes to dating drama, don't mess with Taylor Swift
. If you break her heart, the country music star warns, "I'm going to have to write a song about you."
And the 18-year-old – who performed her first ever European show Wednesday night at King's College London – has already crafted at least one hit out of real-life heartache.
Just before she launched into "Should've Said No," the singer explained onstage, "This is a song that I wrote about a guy who cheated on me."
Any boys behaving badly will also have to answer to Swift's mother. "I don't have a problem ... that she wrote about [that] guy," her mom Andrea told PEOPLE. "He's not allowed to drive in my driveway anymore."
(One boy who may have a current place is Swift's heart? Joe Jonas. And before the country crooner took the stage, "Year 3000" – a song also covered by the Jonas Brothers
– played to the crowd.)
The recent high school grad
also played a cover of Amy Winehouse
's "Rehab" during the intimate show. But Swift's drug of choice? Shopping!
"I went to Topshop. I seriously want to live there," she said of the hip, London-based retail chain. "They would never notice me and I'll be happy forever. I'm so addicted to it. I love it there."
After the gig, mom Andrea gave new meaning to the term "retail therapy." "We might have to go to some shopping rehab," she said. "She's got serious addiction going on right now with London shopping."
Swift flies back to the U.S. on Friday and will resume her tour with Rascal Flatts.
Get an inside look at Taylor's 18th birthday bash!
See Taylor without makeup! RELATED GALLERY:
See other hot country music stars on the covers of PEOPLE!