Manners

We've worked on sign language with Emillia for quite some time now and one day her and i went to the store to get her the fisher price medical kit for her upcoming doctors appointment (which if you don't have this kit i'd highly suggest it! it comes with a blood pressure cuff, band-aid, thermometer, "shot" and a stethoscope plus a little bag to carry it all in)  It was suggested to us by a great friend of the family. Anyway, we went into the store to get the kit so Emmy could do to the doctors  what they would be doing to her. (it works amazingly by the way!) So we go into the store and we cant find it to save our lives, and of course M wants to play with everything else she sees, shes 18 months! What else would you expect? So M is terrorizing the store as im looking for this kit and the lady helping us was sooo crabby. We finally found the kit and M is carrying this darn thing which is taller than she is, we take it to the front counter and Emmy pays for it, the lady gives her back our change and M says AND signs "thank you" (her language is very clear for her age)  the lady just stood there and looked at Emmy for a couple of seconds them M looks at the lady, points to her, shakes her head and says, "NO, you say you're welcome" as she signs this as well............. the look on the lady's face was priceless......... I was very proud of my daughter for using her manners but since when does an 18 month old need to teach a grown adult about manners......?