The first one, Annika and Pinky's catfight. I don't if these two had this planned, but whatever Annika said about Pinky, or at least implied, was right. Pinky does weave tales and play to be the victim to make Annika fall in Shivaay's eyes. Even in that confrontation Annika had with Shivaay the previous night, she was right, Pinky has never respected Annika. But Shivaay is aware of that and he has acknowledged it several times himself. But he has no idea that Pinky is harassing Annika to this extent. If I'm not wrong, when Shivaay came to the living room, Annika looked him straight in the eye and turned back to Pinky and continued speaking in the same resentful tone. If at all she was trying to build the image of an 'evil bahu' in Shivaay's mind, she would have pretended not to see him. As cryptic as it was, I felt she was trying to drop Shivaay some hint (whether Shivaay picks it up or not is a different story). If not, she could have just struck up some baseless argument with Pinky. But she described exactly what Pinky was doing. No lies, no stories, only the truth.
Now the second one, the conversation Annika had with Tia over the phone. Tia asks her if she is sure and tells her that their lives would change forever after that. She doesn't say they would separate. She just says their lives would change, that doesn't necessarily imply a separation. Tia further asks her if she doesn't feel scared. And Annika says, "As long as Shivaay is with me, I have nothing to fear". Let's not ignore the confidence that was on her face when she said that. If whatever Tia and Annika were up to was to lead to ShivIka's separation, that dialogue makes no sense at all. As nonsensical as IB is for the most part, I don't think the writers would throw in such a profound dialogue in that particular scenario for no reason. And also, if Tia really has changed for the better, she would never help Annika in her plans to separate from Shivaay.
And one last thing, from Wednesday's episode, the Annika and Tia's conversation was not shown in full, it just stops at Tia offering to help Annika, we didn't know what happened after that. Now the most obvious assumption would be, Annika would have asked Tia about that video, Tia would have told Annika about Om's apparent illegitimacy and there we go, Annika has the perfect weapon to ravage her relationship with Shivaay. But if it were as simple as that, they would have just shown us that conversation in full. The audience already have been shown the contents of that video, what's there to hide? But if they've kept it under wraps, there has to be a reason. And I for one refuse to believe that Annika could hurt Om to 'protect Shivaay' or whatever. The guy was emotionally extremely weak, maybe still is under the facade of strength that he displays. He resorted to taking drugs because he couldn't handle the guilt of killing someone. His mom's suicide attempt wrecked him to a point he had to sculpt an entirely new and cynical personality, so unlike him, to salvage himself. Let's forget the credibility of the old lady's testimony for now. If that video reaches Om, he won't be able to take it. It would destroy him. Annika letting that video come out in the open, would be indefensible, whatever her justification maybe. Even if that old lady was wrong and that is revealed to the family later, Annika using it to protect Shivaay at any point, would be utterly selfish. She would be pushing Om into the very abyss she does not want Shivaay to fall in. Throwing weight around, being rude to family members, acceptable. But this, a big no. And I strongly believe Annika will not stoop to that level.