Actually, Saransh ka kinda makes sense. Because she is Saransh's mother for all intents and purposes. But that she is not his biological mother is her personal truth to share. In a way, even now, she might trust Ru for Saransh but somewhere she doesn't trust him completely for herself. When she does that, I think she will reveal that truth to him. So, I am not holding that against her.
But yeah, they should tone down her 'main jhooth nahi bolti' because otherwise, it just comes across as hypocritical knowing what we know.
Ya, Saransh truth is a valid case, it's completely understandable from her POV .. but there is no denying the fact that her being Saransh mother is a lie and it will come out in front of Khurana in such a way that she had lied about it all throughout.. Plus lying about Rajeev murder.. In such a scenario.. they can avoid giving her dialogues like 'mein jhoot nahi bolti' because the viewers know that she had said a lot of jhoots.. & eventually Khuranas will also know.. So what's the actual point of that dialogue