Friend I so agree with you. See, this is where Seher has gone wrong...
I was ok until she continued to impersonate Sanam... but AFTER her meeting with Badi Ammi, the kind of thought process that she puts in for her self preservation was lacking in saving Sanam.
1. when she knew Razia has goons, is kinda powerful, why go alone without preparation? Why not alert someone... best bet would be Aahil. Isn't he madly in love with Sanam? Wouldn't he listen?
2. Why did she not think of a plan b with Badi Ammi... tell her if she does not return in so and so time... come back with Aahil and family..?
3. When Razia was asking her to get married to Aahil, why didn't she agree just to buy some time.. surely Razia wasn't getting everything on the same day...
Reasons of above is that she was only thinking of her preservation even at this time.
Also, she is aware that these days Aahil is questioning Sanam's love for him, so chances of him getting angry / mad with rage at Sanam missing from her wedding were high... Didn't she know she acted abominably a day before wedding, shaming the Ibrahim family. Didn't she know Aahil was mighty upset with her... In fact he didn't say but if not for Rehan he was actually in 2 minds about the wedding..
really now, how can folks absolve her of all blame... her not involving Aahil in this rescue operation has cost her sister big time. She knew Tanveer will cook up something . Only Seher knew the threat that Tanveer gave on the day of the wedding... She should have realised ...
Now if Aahil asks why he wasn't involved , no one including silly Badi Ammi will have an answer.