Honest question here: did Raghav say "no" during the night of vāstu-śāstra or did he just say "Pallavi?"
Putting on my parallel dishonest cap now: maybe there's a language in which "Pallavi" is a word for "no" in the context of a kiss that one doesn't see coming.
On a tangent now, maybe Raghav said "Peccavi" and his roommate heard "Pallavi," so he was enthusiastically consenting but she thought she was taking advantage of him?
Obliquely, if Raghav saying that he got carried away by emotions means that we have to fill in that it was his overpowering love for Pallavi that made him use the nearest substitute, and if Raghav saying that what shouldn't have happened happened means that he really doesn't remember, and not remembering means that he was violated, and being violated implies that he said no, and anyway, if Raghav saying that he thought of Pallavi means by default that nothing happened, because Raghav's not forcing himself on his wife makes him incapable of adultery ... we can surely believe that everyone misheard "Peccavi" as "Pallavi."
Also, Pallavi respecting Kirti's privacy and not inviting Raghav to beat Sunny the way he beat Akash is an acute vertex to Raghav asking Kirti to keep his secret from Pallavi who had a right to know.
When I wrote "I don't condone what Pallavi did at all," and "Raghav's behaviour is so different from how I imagine him behaving in my fan fiction," how obtusely I failed to anticipate the rebuttal, "Why are Pallavi's choices defended in the name of poor writing but Raghav's not?"
Back to my orthogonal honest arguments: just as "You said yes last time" is not an excuse to presume consent, "I said no to the kiss" would not be an excuse for someone who goes on to participate in sex willingly while drunk and regrets it in the morning.
Bottom line: Pallavi was wrong to lie to Raghav about infertility, and wrong to hit him with a jhāḍū and a lāṭhī, but if she had fulfilled Milind's warning from when he gave Raghav a ride after the marketplace slap, she wouldn't have to worry about a stepchild now, although sexually transmitted diseases might still be an issue.