Episode 4 [re-watch]

[A Cousin]

To defend Ros even though she is a bitch on wheels for the whole of S5, I think she is as pissed off at the fact that Harry kept it from her for as long as he did than anything else. He doesn't tell her because he thinks she will go to bits over it and possibly jeopardize the operation. Its kind of a slap in the face to her professionally.