If sounds like your daughter is entering the terrible two's, brace yourself! She is testing you to see what she can get away with. I don't know if this is sibling rivalry, if you give her enough attention, then it may not be jealousy., just a toddler. You mentioned that you show her what to do, but she is choosing to do other things, so have you tried discipline? She needs a consequence for her actions to know that it is wrong. Her mind is quite simple now, so try not to overthink it. When she does it, put her in a time out and say we touch nicely or don't touch at all. Make sure the message is clear with the action (time out or whatever method you choose). She will get it
quickly if you are consistent, clear, and firm.