DD behaviour around nephew

[girlmummy25]

My DD is nearly 3 and is generally a good girl however, my nephew is 5 and I dont find most of his behaviour acceptable to my parenting. The problem is that my DD is now copying him and when I tell her off she doesnt seem to care because he isnt being told off and he will just laugh etc so she will do the same.

I just dont know how to keep her in line when she is around him. My sister isnt that great at telling him off and he often doesnt listen.

Today for instance, my DD and nephew were eating dinner and he starts being silly and playing with his food and standing on his chair etc so my DD then copies & I tell her off and move her chair so she isnt next to him, this then leads to a huge meltdown from her and I have to put her on the naughty step, its escalates so much with her than I just end up leaving my mums house.

What can I do? I know kids will be kids but I find it so hard with her when she is around my nephew. Im very close to my sister and dont really want to distance myself over this