Violating WARP or not?
When she chooses the bundle (6,6) when the prices are (6,7), she spends 
\begin{equation*}
6*6+6*7=78
\end{equation*}
The total price of the bundle (10,0) given this price system is 
\begin{equation*}
10*6+0*7=60&lt;78
\end{equation*}
Therefore she could afford the bundle (10,0) if she wanted to. The fact that she chooses (6,6) reveals that she prefers (6,6) to (10,0).

Given the price system (5,5), when she chooses the bundle (10,0) she spends
\begin{equation*}
10*5+0*5=50
\end{equation*}
And the price of the bundle (6,6) would be
\begin{equation*}
6*5+6*5=60
\end{equation*}
Therefore (6,6) is not necessarily affordable if her budget is comprised between 50 and 59. This is why (10,0) is not revealed preferred to (6,6) in that case, and thus there is no evidence that she violates WARP.