Madden and Hilton
Gilbert Flores/Celebrity Photo
03/15/2008 AT 06:30 PM EDT
says she’s ready to hit the road with Good Charlotte guitarist Benji Madden, her boyfriend of a month and a half
, when his band kicks off an international tour next week.
"We’re actually leaving in a couple days for South Africa, so I'll be with him," Hilton told PEOPLE at the launch party Friday for Madden’s new DCMA Collective store in Los Angeles.
But is the heiress really ready for life on a tour bus? "I'm just happy to be together, so no matter where we are, we'll have a great time," she says. After shows in Johannesburg and Cape Town, Good Charlotte heads to Europe and the U.K. before hitting the road in North America this summer in support of their album Good Morning Revival.
At the party, Madden said his favorite part of the clothing line he runs with twin brother Joel
is the collaborative T-shirts they've done with celebrities including artist Shepherd Fairy, Oscar-winning rap group Three 6 Mafia and director Chris Robinson. Asked if he'd consider collaborating with Hilton, Madden tells PEOPLE: "I'd do anything she wanted. I'm a really easy guy to read. Everyone can tell I'm really happy. She's the most supportive [girlfriend], even as a friend, so supportive of everything I'm doing. And I try to be the same way for her."
The couple wore their favorite matching initial rings
from Beverly Hills jeweler XIV Karats at the bash.
Hilton, in turn, gave props to Madden, saying she's a cooler big sister nowadays, thanks to her beau. "My little brother Conrad – he's 14 – loves the line as well," she says. "He skateboards. Benji said he's going to bring him here to go skateboarding [at the store's indoor ramp]. Benji brought up a huge box of DCMA stuff for both boys. They love it."
Even Hilton's sister Nicky agreed: "He's very, very nice."