-Você é danada! Sua atitude também não fica atrás!
You naughty girl! your little devil! (all said in a mischievous way, for example, with a wink or a condescending smile...)
you did outsmart her!
You know how to be a naughty girl, huh? that took the biscuit!
Você sabe ser a garota má, hein? mas essa realmente superou tudo!
I knew that you could be nasty when you want, but that took the biscuit!
You do the darndest things! who would think of writing all that she did to us!
You do the dardnest things! (now I really know that) nobody can ever outsmart you!
And other ways, in different given contexts. Of course.
My above reply is in a different context of that of Breckenfeld previous one. But it´s going, for variety´s sake.