É que vem mesmo a propósito:

"Patricia Henderson Shimm

parent educator and author

Take comfort in knowing that nearly all parents and preschoolers have this struggle at one time or another. Dressing is a good arena for your child to assert her independence, so don't let getting dressed become a battle between the two of you. Instead of letting her see that her behavior is ruffling your feathers, stay calm. Then give your preschooler no more than two choices: She can wear the polka-dot pants or her striped dress. Since many kids this age detest transitions, it also helps to address her reluctance to get changed or leave home. Say something like, "I know you don't want to take off your pj's — they're so comfy. Here, can you please hold your book while I help you put on your pants?" This way you've empathized with her and then used a fun distraction to get the job done.

Children this age don't respond well to being hurried, so if it's at all possible, try not to make mornings a big rush. Instead, wake her up half an hour earlier, or let her help you lay out her outfit the night before so there's less opportunity for dawdling and conflict in the morning. Preschoolers usually love going to school, so you might also try telling your child that if she doesn't get dressed soon, she's going to be late for school and then she'll miss free-play time.

It also doesn't hurt to let your preschooler be in charge of what she wears sometimes. If she wants to wear her ballet outfit every day for weeks, then let her. The outfit will probably fall apart from overuse and constant washing, but she'll outgrow it soon, anyway. A sense of humor helps in these situations. You may desperately want your child to look "put together," but if you step back and look at the big picture, it really doesn't matter if she's mismatched from head to toe. As long as she's adequately dressed for the weather (not covered in layers on a hot summer day or bare-legged in the winter), she'll be fine."

in www.babycenter.com