What Zaki told Aarzoo today holds the key and I feel thats what resulted in Aarzoo going in silent mode in the last scene .. She was silent not to protect Zaki or keep his promise but to protect Sahir and his business here ..
Lets just rewind to what Zaki told Aarzoo today ... He made 3 clear points to her ...
First point .. Samaira mayb lieing about her pregnency and even if she is pregnent , he is not sure if the child belongs to him which is a valid point ..
Second point .. Unless he does the DNA test and is sure about the pregnency confusion , he cannot open his mouth to anyone because Samaira's father is involved in a very important business deal with Sahir ... Now even Aarzoo is aware of this business deal since Alvira told her yesterday about Sahir's only mission ..
Third point .. One small mistake and this business deal might go kaput because if Samaira's Father finds out Zaki is putting wrong accusation on Samaira about her pregnency without any proof , he may well call off the whole deal which will mean Sahir's promise going for a toss too ..
So Zaki wants a promise from Aarzoo to keep quiet till he does the DNA test and finds out the real facts ... Aarzoo promises him to remain quiet ..

Right after this Kurti Apa accuses Aarzoo that she is pregnent with Zaki's child .// Aarzoo instantly guesses that Kurti apa definitely overheard something related to pregnency and so putting these accusations ...
Lets assume if Aarzoo had denied the pregnency saying she is not pregnent with Zaki's child and its a lie , then I m sure Sahir would hv breathed a huge sigh of relief and might hv defended her too like we all wished but at the same time would he as well as Kurti apa not questioned Aarzoo that if she is not pregnent , then who is pregnent because KA overheard the word pregnency ?? 🤔...
Sahir saw them both in hospital and even Kurti apa overheard something about pregnency which Aarzoo might hv guessed it the moment she accused her of pregnency , so its obvious that Aarzoo will hv to then tell everyone who is pregnent or else Kurti apa would hv questioned her further about what was she talking to Zaki on pregnency that she overheard .. right ? ... Suppose she tells Samaira is pregnent ... Then what ?? ... Zaki will b called who will say he is not sure its his child and mayb DNA test will b conducted ... Hearing all this Samaira's father will go mad that his daughter's pregnency here is being questioned and might cancel the entire deal with Sahir , thus breaking his 7 yr old dream
In the end who will b at loss .. Zaki or Sahir or Aarzoo ?? ... Obviously Sahir will loose the deal due to Zaki-Samaria fiasco with Aarzoo telling the truth
Now lets see the alternate situation that was played by Aarzoo today by remaining quiet ... So she took all the blame on herself and even stopped Zaki from saying anything when she could hv well allowed Zaki to open his mouth as he was not bound by any promise .. right ? 🤔...Everyone raised questions on her character while poor Sahir stood there all helpless but still hoping Aarzoo just says one no , so that he can defend her .. I bet he came there to defend her only with a hope that she denies at least once .. But she dint thus hurting Sahir's faith in her even more .. All he could do is give those looks of disbelief and pain to her but could not say anything in her defence for the first time 😭😭 ...
Aarzoo knows well that she is loosing Sahir's trust forever , yet she keeps quiet ... Was it just Zaki's promise that kept her quiet ?? If promise was the only reason , then why she even stopped Zaki from saying anything .. He dint make any promise to keep quiet na ?? 🤔 ...
So the reason is not the promise .. Reason was Sahir's dream .. This business deal which now she knows holds a lot of importance to Sahir after Alvira told her about it yesterday .. There must b a reason why CVs showed Alvira telling Aarzoo about the 1000 crore business deal followed by this pregnency tamasha today ..isn't it ... Aarzoo now knows that Samaira's father is the medium between Sahir and his dream and if her father calls off this deal , everything is lost forever ...
So to protect this deal of Sahir , we see Aarzoo keeping quiet and taking all the blame on herself so that Samaira is not put under the scanner by Sahir which might result in her father calling off the deal

Tomorrow if Zaki gets the DNA report and its proved that the child does not belong to him , then truth can b brought out in front of all and even Samaira's father will not hv any mouth to accuse Sahir or Zaki here since his daughter was wrongly accusing Zaki ... Say if the DNA report comes positive too , even then Aarzoo expects Zaki to own up his mistake and finally tell everyone about his relation with Samaira with proper proofs so that later neither party can accuse each other of cheating ...
Aarzoo remained quiet because she dont want Samaira's truth to come out at this stage when Zaki is not ready to own up his mistake before the DNA test , as it can result in Samaira's father calling off the deal .. Aarzoo will tell the truth when DNA reports r out so that Zaki either owns up his mistake or proves Samaira wrong , so that Samaira's father cannot counterattack Sahir on it ...
And today if Aarzoo denied her pregnency accusations then she would hv been forced to tell the name of that girl who is pregnent , that is Samaira which would result in Sahir's deal with her father getting affected like I said because Zaki is not in a position to own up his mistake without the DNA test but Sam is in a position to go and create a scene in front of her father thus making sure deal is cancelled ...
Sam right from word go looked like a manipulative women who knows well that cards of Sayyara r in the hands of her father .. I wont b surprised if Father-daughter together hatched this plan ... No wonder Zaki had his doubts today and asks her not to tell anyone and then tells it all to Aarzoo ...

So What Aarzoo did today was risky yet smart to make sure no harm is done to Sahir's deal because of Zaki's blunders or Samaira's manipulations 👍🏼...
In the end I m not saying Aarzoo did right by remaining quiet and playing the mahaan card .. Of course she was wrong here .. But in the long run if I see , her silence only will make sure Sahir tomorrow cracks this deal with Rehmaan and Singapore Clients Successfully unless Sahir himself goes on a investigation mode after feeling Aarzoo can never do this which will mean he might loose the deal but protect Aarzoo's honour 😳...Whereas Aarzoo is silent so that he gets the deal even if she looses her honour ...
From precap it looks like Sahir is still in dilemma and trying to analyse which is the real Aarzoo ... It will b interesting to see if Sahir goes for his own investigation here 🤔