"메아리되는 그대 애기는" => Your story that echoes back / Your story that reverberates.
* 메아리(echo) 되는(becoming) 그대(your) 얘기는 (story).
It is only a fragment of a sentence, just the subject part (는 indicates subject/topic).
Also, 메아리 되는 sounds slightly unnatural to me.
메아리치는 (making an echo; reverberating) or 메아리로 돌아오는(coming back in an echo) seems better.