He already knows that."Yukkasen" means "not to tell things to someone".
Please tell me~I done told you, "'ain't gonna tell" ya know!!
She used two Kagoshiman words:
やっで (yadde, "ya know") is a counterpart of standard Japanese word だから (dakara, "you know").
ゆってる (yutteru, "I done told you") is a counterpart of 言ってる (itteru, "I told you").