I agree with MintyBlue. Somethings are complicated. They exist in a murky area beyond traditional norms of right and wrong.
Cheating on someone and betraying their trust will always be wrong. Breaking up a family and hurting innocent people will always be wrong. But falling in love is not wrong either. Life changes. People change. People fall out of love with their significant others and fall in love with other people. Living a lie is not healthy for relationships either. Forcing yourself to be with someone you no longer love will keep making it worse. Individual happiness is just as important as the happiness of spouse and children. The other person is also a human with feelings, emotions, and needs. When you fall in love outside of marriage - no matter what path you take - people will be hurt.
I don't think Geet tells Aditya to let his mom off the hook. In fact, he has already punished his mom for her transgressions. He has spent years letting her know he is angry and hurt by what she did. Geet makes him realize that his mother was only human. Forgiveness is not letting people off the hook, but giving yourself closure so you can move on.
Monica has Chandler do the same for their wedding. Chandler grew up in a toxic family where both parents cheated and sniped at each other. But Chandler's father was also living a lie leading to some of the toxicity. Chandler feels betrayed and hurt by his father and punishes him. Finally forgiving doesn't let his father off the hook, Chandler has punished him his entire youth and adult life. But forgiveness actually helps Chandler get closure and move on. He can now enjoy thanksgiving again with friends and loved ones. He's happy at his wedding to have his parents there just like Monica's. He overcomes his lifelong commitment issues and becomes ready to become a father himself.
1