Emphasis is put on the second "boing" and the gusto with which that "boing" is delivered is meant to underscore the sincerity of the speaker's resolve that his/her statement is the undeniable truth.
This phrase is especially useful after successfully completing an act which others have claimed impossible.
Speaker 2: "I can & I will."
(Speaker 2 successfully dunks.)
Speaker 2: "Sha boing BOING!"
1) A beautiful woman, with a nice body & face
2) The act of sex (porn, fucking)
3) A sexy picture
Boy: Google 'Rihanna fucking'... Minutes later, "Sha Boing Boing"!!!!............... Fap Fap Fap
(Btw, Rihanna is talentless, i just used her because she a whore.. :)