I have a picky eater?

My daughter is nine, and she eats practically no variety in foods - she'll find one food she likes and wants it every day for months. Usually these foods are pretty healthy - this time around it's mashed cauliflower, which I know isn't at all bad for her, and last time it was spinach (she wanted spinach salad, sauteed spinach, spinach parmesan, spinach EVERYTHING) - but she only eats ONE thing, for EVERY meal. Is this okay or should I try introducing different foods?