Khusiya, is an uneducated and simple small town daughter-in-law, who has been subjugated to mental torture from the time the poor cow has been married. Her evil, cunning mother in law has kept her submissive and to top that, the very stupid, obnoxious and blind husband of hers, has also AWAYS time and again made her apologize and feel sorry and feel small in front of the rest of his monstrous family. This woman, has NOT known any other way of being, but being this submissive. IT is so easy for people like us to sit and watch the show from urban cities , not knowing any reality about how small town families are still rooted in a lot of this kind of archaic tradition of daughter-in-law being treated this way. Of course I blame her for always being too dumb to see how her mother - in law makes it a point to humiliate her in front of her husband and for never standing up for herself. But, imagine if she does raise a voice again Shanti, her husband is going to throw her out. From the mind set she comes from, where does she go? She doesn't have an education or a work skill to last out independently in the world apart from being dependent on her husband. She doesn't even know she can fight legally against her MIL or for the custody of her kids. For her, if she is thrown out of her house, it spells death, nothing else. So for some one in that position, there is no hope but to keep being submissive and look at it as the norm for how DIL should be like. That's probably what her mom passed on to her too.
As for her lashing out at Riya, Of course she is wrong, but for god's sake, the last thing that it can be reasoned to is her being jealous. The thing is, she is battling a lot of emotion inside of her, since the time she and Raghav have had a fight over the money. She has not been able to speak to him after thanks to MIL and her effed up plans of astrology and fasting and what not. To top that, Shanti has put so many doubt about Riya in her head, about her being modern and taking Shivam away from her and what not. Today, she instilled an absolute crippling fear in her about Shivam's misfortune thanks to the fast being broken. IT was simply a lot of pent up emotion that came out. And to top that, for the first time in her life, her son, the only one who supports her, answered back. ( he was right in his position to do so) but for her, it basically was a crumbling defeat, because her husband never stood by her, and today she thought thanks to the new wife, her son has spoken against her too. I actually felt bad for the poor thing because you can see how everything was evilly planned by Shanti, to cause this pain to Khusiya.
She has by far tried to always be very nice to Riya, but she is not a modern, or broad-minded person. She has a narrow outlook about what a DIL has to do, and she is also easily convinved by others to change her mind about things. Right now her relationship with her DIL is being ruled by SHanti. So she doesn't understand Riya herself, it is what Shanti tells her that goes through to her, which is basically a negative image.
If anything, I hope Riya ( the so called modern and educated, but really stupid and not street smart person at all) ends up understanding the games Shanti plays and understands the ill treatment of her MIL in the house and ends up being her support and empowers her to stand up for herself against her spineless husband and cunning SIL and MIL. That's the least you can hope from someone who claims to be educated. So far, Riya has proved to be stupider than illiterate Rani also.