Confidant and Confident

Don't confuse the nouns confidant and confidante with the adjective confident.
 

The noun confidant refers to a person (usually a trusted friend, family member, or associate) to whom secrets or private matters are freely disclosed. A confidant may be either male or female. A confidante is female. 

The adjective confident means certain, bold, or self-assured.

• "He was my soul mate, my confidant, my hedge against loneliness. I needed him. I felt lost without him."
  (Betty Berzon, Surviving Madness. University of Wisconsin Press, 2002)
• "Eleanor began to shed her timidity. On her honeymoon in Switzerland, she had feared scaling the peaks and watched as Franklin marched off with a glamorous hat maker. Now she hiked mountains with long, confident strides, outpacing everyone else."
  (Joseph E. Persico, Franklin and Lucy. Random House, 2007)
• "Going past the room occupied by the young missionary, I smiled upon his door, which was shut, confident that he was inside hard at prayers."
  (J.F. Powers, "Death of a Favorite." The New Yorker, 1951)

• "Today the forms confidant and confidante predominate in both American English and British English, though confidante is falling into disuse because of what is increasingly thought to be a needless distinction between males and females. Despite the poor etymology, one can be confident in using confidant (/kon-fi-dahnt/) for either sex, as it is predominantly used in American writing."
  (Bryan A. Garner, Garner's Modern English Usage, 4th ed. Oxford University Press, 2016)
• "Confidant(e)/Confident. As with all words ending with ant/ent, the former is a noun and the latter an adjective: He was so confident, he did not need a confidant in whom to confide his fears."
  (John Seely, Oxford Guide to Effective Writing and Speaking. Oxford University Press, 2013)

(a) Congressional leaders stood in a little cluster, wearing the aggressively _____ expressions that politicians put on when they face a pack of reporters.

(b) My mother is my best friend and _____.

(a) Congressional leaders stood in a little cluster, wearing the aggressively confident expressions that politicians put on when they face a pack of reporters.

(b) My mother is my best friend and confidant (or confidante).