she may seem shy and ordinary right now, but give her a couple more years - she truly is a diamond in the rough
someone (or something) that has hidden exceptional characteristics and/or future potential, but currently lacks the final touches that would make them (or it) truly stand out from the crowd
"she may seem shy and ordinary right now, but give her a couple more years - she truly is a diamond in the rough" What is the definition of "diamond in the rough"?