Carrying on like the couple that they’re rumored to be, Lindsay Lohan and Samantha Ronson were spotted celebrating Sam’s 31st birthday last night in West Hollywood, California.

The “Labor Pains” actress was especially enthusiastic about her girlfriend’s big day, planning an amazing party at Matsuhisa sushi restaurant. And she didn’t leave anything out.

Partygoers enjoyed balloons, ice cream (courtesy of a genuine ice cream truck) and party favors as rumors of a possible LiLo/Sam engagement abounded due to Lohan’s left-hand bling.

Among the guests was Nicole Richie, who looked lovely in a white blouse teamed with a high-waisted black skirt complete with black strappy gladiator-style heels.

Gossip Girls

Enjoy the pictures from Samantha Ronson's 31st birthday party (August 7).