Written and first recorded by Jules Shear (1985).
Hit version by The Bangles (US #29/UK #31 1986).
From the wiki: “‘If She Knew What She Wants’ is a song by Jules Shear (‘All Through the Night‘) released on his 1985 album The Eternal Return. The song was later and famously covered by The Bangles on their 1986 album, Different Light. Shear’s song was originally written in the first person, essentially a love song; the Bangles rewrote the lyrics in the third person, rather than change the subject’s gender.”
The Bangles, “If She Knew What She Wants” (1986):