I don't know whose plan it is. But definitely it's a plan.
My speculation is this
Nagini's plan: [lets call her plan becoming Mrs SSO]
She overhears aniomru convo about not having a real fianc. Remember the Shakira dialogues of aniomru outside Shivaay's bedroom? So she brings TB. But TB double crosses nagini. I will explain that in Shivaay's plan. Nagini wants to become Mrs Shivaay Singh Oberoi. So that's her main plan and will have lot of sub plans to achieve the main plan.
Shivaay's plan: [settle old score with mophead]
He has got some connection and an old score to settle with Mophead, do you guys remember? Nagini's brother who was suppose to be parallel lead. So Shivaay gets close with Nagini for settling score. But lucky for Shivaay Nagini comes in handy with another plan as well i.e. to make Anika jealous. She comes in handy for all of Shivaay haq, faraq game plans as well.
And when TB comes and confesses to Shivaay of Nagini's blackmail he uses it to the fullest for his main plan. And while settling score with Mophead if he can get back Anika it's well and good. Throw one stone and get two mangoes type. For TB it was love at first sight. So TB wants Anika to be happy. You see it's called true love.
Omruriya plan: [Jealousy, go with the flow, ehsaas]
These four love their bade baiyya and babhi so much and want them to get married and live happily ever after. They want them to loose their tadi and think with their heart and not with the mind. So they are constantly planning and plotting. For shivaay and Anika to become Shivika.
Pinky's plan: [get the manoose Anika out of Shivaay's life even if it means Nagini is her daughter in law]
Keep insulting manoose Anika about her low class life, and flip between taunting Gauri and being friends with Gauri.
Gulneet's plan: [the best plan ever]
Drive the IB fandom crazy so that everyone losses their marbles and regret the day they started watching IB
My Plan:
I was planning to watch it till August end and decide. After the engagement of Shivika in the dark and Surbhi neck sprain decided to quit the show till the reunion. But changed my plans again to watch it till August end and decide further course of action. I might change my plan again depending on the trp of my headache and stress this IB gives.
PS: this is just a fun post. Not to offend anyone.