Uh, you'd be wrong on that one, man. Usha comes from Telugu Brahmin stock, complete with a family tree that goes back several hundred years and has more than few wealthy members back in India. Her stock is as high caste/jat as it comes.
Most people don't really get the social politics of India. If Usha seems disdainful of pajeets, it's because she comes from the Dravidian side of India, when most of the diaspora/desis comes from the Hindustani side (it should be noted that Vivek, as a Tamil would share that distrust of Northern Indians). Caste/jat really only matters inside India, but the ethnolinguistic and religious divides are far more lasting in the diaspora. Either way, I don't think it matters much because she's hella assimilated to American norms outside of her private religious and dietary practices. If anything, Tulsi, who isn't even subcontinental at all, carries a lot more Hindu cultural baggage than Usha does.