Translation for German idiomatic phrase

Hi,

first - I am new and glad having found the place.

Then - there is a German expression I wanted to translate into English. For those who might know German: "Sie hat es faustdick hinter den Ohren."

This means she is a clever person, somebody who might come up with ideas and actions you wouldn't expect, sometimes perhaps half illegal or sassy. It is a bit reproving but in fact more acknowledging. Hard to describe....

Now I searched for translations and found:

"She is a deep me." Never heard that and when I asked a native English speaker he told me he never heard this exact expression. Maybe it should be "She is a deep one."

"She is a sly dog." Might be ok as translation but as I am talking about a beautiful classic lady it seems not appropriate to me.

What would be your recommendation?


Edited to add (cause i got 3 messages from a critical user): I _have_ searched the internet but am not sure about what I found - therefore the question here. And please forgive if my grammar and vocabulary is not perfect - I'm no native English speaker.