i think the Ml would turn out to be fake eventually
as far as what u said is concerned
1- the CVs might actually re show the scene in a different way...for example;when shivaye was looking she was falling he turned to go downstairs to see what happened to her (in the mean time the mattress and rudra were there...it doesn't make sense but what does theses days???)
2- i think the CVs might get a memory loss about this bit as they alaways do
and if they don't then there's another explanation : when she said 'pati parmeshwar' she was near Tia's room so perhaps she wanted to assure tia that she actually lost her memory
in addition...Annika Would assume that Tia and Swetlana would be watcing her all the time (specially at first) to make sure that it's not a plan to trap them (since they know that anika already suspects Tia & Swetlana individually )
3- as far as the engagement goes I have 2 theories:
*judging from yesterday's episode i don't why but i felt the shivaye knew that anika was faking the ML...from he's words to his tone to the why he was asking her about her not caring about his marriage... and if this is the case it means that anika proposed Shivaye to marry Tia thinking he would refuse but with his anger he actually agreed which led to this mess
**they're both being stubborn ...she wants him to accept her as his wife so she's pushing to his limits...and he just wants to see how far can she actually push him