Just when you thought it couldn't get any more sickening...

... Spencer Pratt and Heidi Montag are engaged!

The 23-year-old Pratt popped the question to the 20-year-old Montag on Tuesday night at the Bacara Resort & Spa in Santa Barbara.

An Us Weekly source close to Heidi and Spencer reports they are thrilled, and adds: "She said 'yes.' She's over the moon!"

Expect staged photos of their happy engagement any second now.

The stars of The Hills, whose gross courtship was chronicled last season on the hit MTV reality TV series, have been dating for eight months.

Spencer Pratt purchased a diamond-encrusted platinum band with a pink stone on Monday at Ice at Brentwood Gardens before presenting Heidi Montag with a bended-knee proposal, according to a source.

An eyewitness at the store says, "She was trying on tons of them and they looked really happy!"

Heidi was formerly a close friend and roommate of The Hills star Lauren Conrad until Pratt caused a rift between the two and lured Montag away from LC's pad and into his dungeon.

Soon after moving in with Pratt, Montag got a boob job and nose job, while Audrina Patridge moved into Lauren's apartment in Heidi's place.

The couple has not yet set a wedding date, but don't think the PR guru won't keep us well aware of it throughout the planning.

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.