Yea - but all that in last 10 mins of the last mission? Also, Sela was supposed to be antagonistic to Tal Shiar, but now she works with Iconians? It's just confusing. Also, the gates are confusing too - these Romulans have the best travel system of the galaxy and they can't call reinforcements thru it? Why is a random arch between two buildings an iconian gate? How did you survive a torpedo blast standing 5 meters from it? It's just odd.
From my point of view, Sela wasnt there to back to Tal Shiar, as much as she was there to stomp out the out of control fighting the Tal Shiar had caused.
From Selas point of view I could see her deciding she had allowed the Tal Shiar (a group she butted heads with...remember she attempted to assainate the leader of the Tal Shiar in the past and was vanquished for it) to go on for too long. She hated the Tal Shiar and figured them and the Reman rebellion would slug it out until both were severly weakened. Or one was destroyed and the other was weakened, either way shed stomp out two RSE enemies at once. But once the Federation got involved she had to make her move.
From what I could tell, she was being kidnapped by the Iconians. Obesik talks about how the Military is searching for her after you talk to him again at Haakona. Which hints she had nothing to do with the Iconians, but they took her possibly in an attempt to punish the Romulans. Since her disappearance, a number of different groups in the RSE has begun fighting for power.