Kanye West and Kim Kardashian
10/28/2013 at 12:30 PM EDT
It's a weeklong birthday celebration
for Kim Kardashian
, who is still reeling from the excitement of her surprise engagement
to fiancé Kanye West
"I'm marrying my best friend," she told PEOPLE on Saturday following West's concert at the MGM Grand in Las Vegas.
Kardashian said the engagement came as a shock. "It was a complete surprise. I had no idea. I was shaking the entire time – like, is this really happening? It was an out-of-body experience," she said.
And while Kardashian, 33, and West, 36, have barely had time to even start thinking about planning a wedding, there is one decision that is already made: She says stepdad Bruce Jenner, who recently separated from her mom Kris
, will be the one walking her down the aisle.
"Of course he will. [Kanye and I] honestly haven't had a moment to talk about [the wedding] or even breathe, but whatever he wants!" she said.
Reporting by AILI NAHAS