It's a good thing we're behind we get to see what a mess the creatives have made of this storyline. Manav clearly explained to Archana about how he learned that jerk set her up, Varsha had her suspicions about Manju then there's the fact Ajit is not the most credible person.
The seperation could have happened had it been shown that Archana not believe what she hears, remembering her conversation with Manav about how he knew that jerk. Plus, given the conversation that Archana had with Manav the day before the drama started it makes no sense as to why she doesn't even try hearing him out.