What's the name of this band?

okay..so the lead singer is a girl..im pretty sure they are from england..i remember the girl who sings has a lisp..and i cant remember the song or name of their band...i just know they are like cousins or something..the group members...and its sorta like popish rockish...the lead singer has fair skin..she has straight blonde/light brown hair i think..from the video i saw..and there song was played on the n..one time..anyone have a clue?