'Hills' Co-Star Stephanie Pratt Bets Spencer And Heidi Will Last

Spencer's sister says the couple will be together 'forever.'

HOLLYWOOD, California — Although it may be the worst-kept secret of the week, Stephanie Pratt is still being coy about brother Spencer's impending nuptials to his longtime love, Heidi Montag, this Saturday in California.

Her weekend plans include "probably just going to the beach," she told MTV News at the Paley Center for Media event honoring "The Hills" at Arclight Hollywood's Cinerama Dome Tuesday night.

But Pratt was quickly reminded that everyone already knows the pair will be marrying on Saturday — Lauren Conrad has already said she's not attending, and Audrina Patridge told us she's got to go dress shopping. Instead of being cagey, Stephanie should just spill — or at least tell us what she's going to get the happy couple.

"They haven't gotten me a birthday present, and I still don't have a wedding date confirmed, so once I get an invitation ...," she said. "I'm thinking something from Brookstone, something practical."

Stephanie seemed to have one item in particular in mind for them. "A solar phone charger," she said. "It sounds amazing."

And although Heidi's mom, Darlene, gave the pair a six-month expiration date after their elopement in Mexico last year, Stephanie has a more positive view of how long Speidi will last after their full-on official wedding Saturday.

"Forever," she said. "I would bet $10,000, and that's so much money for me."