Im pretty late for this but she says “헛소리 말고 너네 별로 꺼져” which i assume is translated pretty accurately as shut your trap and get lost. While the first part “헛소리 말고” means something along the lines of shut your trap, the second part “너네 별로 껴져” i guess could literally mean “screw off and go back to your stars” as “별” means star (the kind in space). I assume this is why she thought their alien identities were exposed.