My Little Thief (in training)

Today I went to return a rented movie and to pick up a new one.  Great story so far right... really interesting I know.  While I was checking out the new movies and paying for them, Emma was standing there eyeing all the candy and treats, selecting her favorites and then putting them back at my request.  She had grabbed some chocolate covered pretzels, and asked for them.  I told her we had pretzels at Kayla's house she could eat when we got back.  I guess this wasn't good enough for her, because as I grabbed the movies and headed for the door, the employee made a little sound like "uhhh?", which caused me to turn and see Emma right on my heels carrying the bag of pretzels.  I guess she chose not to hear me when I asked her not to grab anymore treats.  Do I need to start worrying yet?  Either that or I could train her to take something better than pretzels.