proud as a peacock
Having a very high opinion of oneself, filled with or showing excessive self-esteem. For example, She strutted about in her new outfit, proud as a peacock. This simile alludes to the male peacock, with its colorful tail that can be expanded like a fan, which has long symbolized vanity and pride. Chaucer used it in The Reeve's Tail: "As any peacock he was proud and gay." [1200s]