Kristin Cavallari – Legally Blonde at 21!

Cavallari, who celebrated her 21^st birthday at LAX nightclub in Las Vegas on Saturday night, was all smiles as she downed champagne Lindsay Lohan-style (straight from the bottle) while dancing to hits like Soulja Boy.

Kristin Cavallari: Photo Credit: Judy Eddy/ WENNBut which Laguna Alumnus was the only friend to make the guest list?

That would be Alex Murrel, Kristin's longtime friend from home.

Kristin spent most of her big night chatting up former flame, Matt Leinart, who was conveniently at the same club - but apparently not for Kristin's b-day bash.

And who didn't make the guest list?

Kristin's other former flame Stephen Colletti and her rival from Laguna Lauren Conrad were M.I.A at Saturday night's party - although that shouldn't come as a shock to anyone.

Now that Kristin's legal she can take partying to the next level.

Wonder how long it will be before she gets a DUI...