My Dress Prob

Hi, i have a prob my cousin n i r sharrin a quince cuz were only 4 months apart!!! but we half 2 have the same exact dress 4 the whole twin like thing 2 work cuz we look alike!!! the prob is shes like a good couple sizes biigger than me n the dress we need to pic we both half 2 like n it has 2 flatter both of us but because shes bigger than me she doesnt like ne of the dresses i pick!!!plz help we normally agree on every thin but not this so i need plz help!!!