i was also thinking abt it wen did she get da time 2 change da letter. lagta hai vansh ne paani laane mein der kar de hogi kyunki voh ti icchaki ke pyaar mein khoya hoga 😍(jab taps ne chakkar aane ka natak kiya iccha ka letter dene se pahle)
Well you see it's quite simple.
When Vansh went to get her water or juice and Vamp saw the letter on the table, she, didn't have a chance in a million to get it because he came back so quickly. So she hid - possibly behind the sofa. Most probably Vansh then looked for her and then when he went out of the room, she quickly took out some of the pages and changed Veer's name to someone elses or she crossed it off entirely and she may have had the chance to also add her own fabricated nonsense to Icha's letter. But while in such a rush she may forgotten to cross off Veer's name in one paragraph.
In the mean time, before Vansh left the room, he may have seen part of her clothing or her hiding and knew something was up that was probably why he wanted Veer or he was completely clueless 😆.
Either Naniji is going to paste, the remaining pages of Icha's letter with the photo of Veer & her or on the wall of the marital chamber, or Vansh (or someone else) will find out the truth before their marriage and together with Veer, and Takur they'll try and sort out this rotten Cachumbar's mess.
In the mean time, relax, have some tea and enjoy the sun on a nice Spring's day, go out for countryside walks... and don't bother getting so anxious over this melodrama! 😃