Need help with a behavior my 17 month old is starting to develop.

I have a daughter(my one and only) who in the past few days has starting smacking herself in the face whenever she gets in trouble. She doesn't hit herself hard but it is unusual behavior for her as she has never done this type of thing before. Me and wife do not spank or hit her often. She will get a light smack on the hand or butt if she does something bad repeatedly. I'm not sure if she is picking this up from another child in her Sunday school or one of her cousins. What is the best course of action or proper way to put an end to this behavior in an effective way? Any tips or helpful comments would be greatly appreciated. via /r/Parenting http://ift.tt/2h23EXh