I'm not sure specifically what the 'khushboo mein base khat story' is as it could be a very specific or personal story. It might be a story that is centered around a character named Khushboo and something related to a letter (khat).
A third possible theme is friendship. The 'khat' could be from a friend of Khushboo, and the story could be about their relationship. It could show how the letter affects their friendship, whether it strengthens it or causes some sort of conflict.
The story of 'tere ishq mein ghayal' is likely to revolve around themes of love and its impact on the characters. It could be that the main characters are caught in a web of emotions where their love is tested. There might be elements of sacrifice, passion, and perhaps a touch of mystery or drama. But without having actually seen or read about it in detail, it's hard to give a comprehensive summary.
Honestly, I have no clear idea. It could potentially be a poetic or metaphorical expression, but without further clarification, it's hard to say for sure.
Someone who has been hurt in love might say this. For example, a person who has just gone through a difficult breakup. They might feel cynical about love at that moment and express their dislike for love stories as they remind them of their own pain.
This could also be a very personal statement. It could be that in their own life, they have witnessed a love story that ended badly, like a relationship between two people they knew that ended in heartbreak or betrayal, and thus they say they hate love stories.
I'm sorry, I haven't read this novel so I'm not sure about its exact content. But from the title, it might be about life ('zindagi'), love ('mohabbat') and some sort of pleasant essence or feeling ('khushboo').