Episode 6.4 [Re-watch]

[Silktie]

I agree that was the hook they used to catch her, but last episode the Yalta leader explicitly tells her they don't know where Zaf is, but that they think the Americans are involved. In this episode Harry initiates Operation Zebra to find out what happened to Zaf, so Ros no longer has the excuse that she had to take matters into her own hands because no-one else was doing anything to find out what happened to Zaf. I have no problem with her trying to use Yalta to find Zaf, but she could have reached those objectives by becoming a triple agent - by telling Harry and the team what was going on and using Yalta to get information - instead she hides Yalta from the team and actively betrays MI5 by giving Yalta the documents they copied from Bob Hogan earlier.