My lucky daughter has a lot of clothes but she refuses to wear anything other than jeans. Ok, I got through that, now she is going behind my back, rifling through the dirty clothes to pick out her wardrobe. There are, maybe 3 shirts she will wear and even though she has a lot of jeans, she picks dirty ones. I don't want her going to school in dirty clothes. I punish, but apparently not the right way, because she keeps doing it.

Don't punish. Punishment causes rebelion and aggression.
Understand her and help her use only one pants cleanly. Wash it and give it back to her clean same day. Don't worry. This is normal. Kindness is always the answer.