About Ram : sure, to see that he is responsible for what Nuts is today is such a shame. He admits it himself, he never raised his voice while talking to her and he even scolded his step mother (Nuts' MOTHER) when she tried to give her some senses. This is such a stupid way to educate someone. He spoiled her and only see her good points. Nuts is a besharam girl, she almost cheats on her fiance, she has a highly image of herself, she counts on her brother name, money and reputation for permitting her to insult badly other people. This is the real Nuts, the one Ram doesn't see.
Coming back to Ram i think that he is a very nice guy and he was very touched to learn that this whole family was left alone when his dad died. He made a big place in her heart for Choti, granting any of her wishes, knowing that he could always take care of the consequences. Because she became someone "famous" too (in the fashion business) he now thinks that he did a perfect job making her grow up so carefree. She clings onto him like he was a teddy bear (no pun intended😆) and maybe he thinks that she acts like that with everyone, which she obviously doesn't.
I'm okay with the fact that he was mad at Kartik, but why could his sister act like a vulgar call girl (he knew that she was partying and drinking alcohol i guess) and why should Kartik be responsible all the time, he is her HUSBAND, not her TOY. He is the same age than her and can make mistakes too.
About Priya : She is the most responsible and cold minded person it seems. I was truly disappointed when she almost said "thing" naming ram at ayesha engagement; but today when Kartik said that Nuts (her future sister in law) was insulting her enough to make him go mad, she didn't falter at all. She took it as it was, and continued blaming her little brother. I think it's extremely well handled by her.
The thing is she screamed (too much for me🤢) at him like he was the most detestable guy on earth. How could she forget after this one mistake how nice he actually his. He is the most sensible guy ever, very intelligent and all this thanks to her. So from my point of view she should trust him. Yes, he slapped Nuts, yes this is bad. Does that mean that he is a bad guy? No.
She knew that Kartik was going to "rescue" Nuts, then Ram came saying "he slapped her in front of people when she was at a club" : this sentence is yelling to my ears "she got slapped while she was partying". If Priya heard that too then she can conclude that Nuts was tricking Kartik, he got very worried over an incident that was in fact a bad joke !
The main point is that she is right : hitting a woman is stooping low, acting without thinking is bad. But she should have listened to him too (and not only ram's version), trusted in the man she raised, and been able to see that Nuts played with him badly which is as worse as the slap she received.