Teresa (Barbie)
Teresa Rivera is a Mattel fashion doll who is marketed as one of Barbie's fictional friends. Teresa debuted in the "California Dream Teresa" doll in 1988 and since then, she has been Barbie's most frequently featured female companion in the toy line (next to Christie). As of 2006, Teresa is one of Barbie's core friends in the Barbie brand along with Summer, Nikki and Raquelle.
In the movie Barbie and the Diamond Castle, Barbie states that Teresa is officially her "best friend", but this fact is modified by Barbie herself when in Life in the Dreamhouse she states that all girls Teresa, Nikki, Summer, Midge, Raquelle & Grace are all her 'BFFs'.
History
To counteract the criticisms that Barbie was a sex symbol, Mattel was compelled to issue companions for Barbie. Some of these are her boyfriend Ken, the African American Christie, Barbie's cousin Francie and Barbie's little sister Skipper. Midge appeared in 1963 and was marketed as Barbie's first best friend. Midge was discontinued in 1967.