This is a clip from the 90210 episode "Unmasked." In it, Naomi complains about her fake relationship with the son of the CU dean.
Added:
The Halloween episode of 90210 is titled "Unmasked." Watch the official CW promo for it here and now.
Added:

90210 Season 2 Episode 7 Quotes

I am so sorry that you're such a sexist ass.

Ivy

Naomi: I can't be distracted by rock-hard abs and thighs that have driven countries to war.
Adrianna: What country has ever been driven to war over thighs?