She always acted snobbish around her classmates, looking down on them and refusing to socialize with anyone she thought was beneath her.

The noun form for the adjective snobbish is snobbishness.

Lexi was being kind of snobbish to me.

Snobbish does not have a prefix. Although, its suffix, is "ish".

'Snobbish' is an adjective meaning superior, arrogant, stuck-up, patronizing, condescending, snooty, and/or pretentious.

Example - He acted snobbish when he was introduced to her.