I found what prerna said perfectly acceptable. She said that bajaj is an understanding person but what about Anurag, did what happened in the bathroom not cause problems for him with komolika? It was totally legit question since prerna knows what sort of a person komolika is. And even though Bajaj and prerna are not a married couple, this fact is known only by them. And let's not forget that prerna is doing this whole Mrs Bajaj stunt o ly so that Anurag thinks she has moved on in her life. So her telling him that she has an understanding husband but what about his wife is totally in line with her idiotic badla ideas. 
I really didn't find that mention of Bajaj out of the blue or monumental. . It was just a passing mention which had no special impact or meaning.