I think Cosima feels like she's being held back because she's unwilling to let herself get caught up in the drama of what's going on. Right now she's more interested in putting the moves on her moniter.
Well considering the pace of the story, she's being left behind. When we first met this clone, I thought she was interesting, kind of the nerdy one of the bunch. The only problem is we've gotten so much story with the other clones that the Cosima side feels like a standstill ever since she went to Minnesota. I do think it's interesting that she might go with Dr. Leake (And maybe even turn against the clones, as this episode might have suggested) but again, the pace of the story makes her part probably the weakest so far.
Gotcha, I think the reason is, like you said, she's in Minnesota. All the action is happening where Allison and Sarah are, it's kind of hard to make a character interesting when the few times she interacts with the main character is through skype.
I would find it interesting if she joins up with the baddie organization and decides to try and hunt the other clones. That would make her character more interesting, I think.
Also, speaking of the other clones, perhaps with Season 2 this will open up and we'll find out it's a global project and there are a hundred clones running around. I'd love to see more, cause I'd love to see Tatiana expand and play even more roles.