Britney Spears, along with her mother Lynne, hit West Hollywood's Yatai Asian Tapas Bar last night. Tucked away on Sunset Boulevard, the inexpensive sushi spot (a la carte sushi, sashimi and hot dishes range from $3-$12) isn't usually a star haunt.

Us Weekly reports that Spears entered around 10 p.m. not looking her best, but "she probably thought no one would see her," a source tells the mag.

And who should she encounter? Ex-boyfriend Justin Timberlake and his actress girlfriend Jessica Biel.

Biel, 26, was "looking gorgeous," to the possible chagrin of Spears and likely delight of Timberlake, both 27.

And how did the run-in go down?

"Jessica and Justin looked to be slumping down in their seats to avoid [Spears]. She left 30 minutes later," the spy told Us.

Was it the sushi?

The witness also says Timberlake and Biel left shortly after.