Mexican-Spanish slang for a white girl or light-haired girl. It is a jargon from Mexico that is also used by Chicanos within the United States. English-language speakers who are not familiar with the origins of Spanish words (or don't care to become educated about them) can become misinformed into believing that one culture's mumbo-jumbo is widely accepted by other Spanish-language societies. Guera (or Guero, for males) is not a word that is familiar among native-Spanish speakers from countries such as Cuba, Santo Domingo, Puerto Rico, Chile, Argentina, etc.
Esa chola es una guera.