A lot of things in this show are convoluted right now and needs clarification so, can't state firmly about everything but, will be specific with my rant which is the lines in bold. I wanted to do this rant but, it took time So, this reply isn't specifically to you, I wanted to do this as a general post but, this may answer your questions/disagreements so, decided to post this as a reply as some parts are specific reply to your reply.
I agree with the rest. I agree with you disagreements as well. Yes, I was wrong about Viaan, just saw the episode properly (didn't watch today's).
From the very beginning, I found Katha to be very stupid in the regards to money collection as it was portrayed by the writers. I found weird that she rejected Aniruddha's offer because its no from Earthcon, its her morality. Later, writers revealed all the legal repercussion things associated with accepting this offer. So, I ignored it like WhAtEvEr, maybe she thought about legalities and it wasn't shown on screen. They only showed the morality part because audiences will like a character more whose morality is above everything else. If they showed Katha taking bribe from Aniruddha, all of a sudden audience's morality and will wake up because a character thought humanly and made a human action .
Now, coming to NGO, Katha won't be the first one to be skipping lines through NGO. All who seek NGO aren't poor, most of them are middle class as well who can't afford the expensive treatment of cancer. Many bribe NGOs but, it rarely works. Most of the times, NGO lacks funds and NGO isn't gonna randomly distribute crores to random children. If Aarav's case is sensitive so will be the case of a fully grown 22 year old man who is suffering from the same disease. Practically speaking, If I had a crore to give for a treatment which actually completely heals this terminal disease (no severe complication left afterwards), I will save 22 year old man. He is young, a lot might have been invested into his upbringing and education, It will all go to waste. Also , 22 years of memory vs 8 years of memory, I would like to save 22 years of memories. So, I found nothing wrong from her from backing out from NGO. Whose sob story NGOs are goona listen to, they have plenty and more gruesome stories to listen than that of Aarav. Her backing out of NGO was completely practical. I remember, she said something like that my Aarav's case is just a file for them and there are countless more files waiting in there. But, makers had to again show - look how morally good our FL is, she is thinking about others . Unfortunately if they don't show it like this, people aren't going to sympathise with her. They have to mould her otherwise practical decision into morality display. Although, there was nothing wrong in trying to prioritize her file in NGO to only see it fail because of the reasons she said.
Unfortunately, truth is that audiences love to see the ML or FL with moral high ground although, to get out of a terrible situation, they will give human solutions but, once those human solutions are executed which makes them abandon their moral grounds, they will immediately bash them. This is the truth and that's why all the ITV shows have doormat ML/FL who have insanely unrealistic moral high grounds. I would apologize that I used the word audience which is a generalizing term but, this doesn't include all audiences and not specific to this show. Right now there is much more wrong with Katha than just this.
Now, question is that why Katha broke in 5 months compared to the 2 years. I Don't know. Breaking points are indeterminate. If I hammer a Iron rod, continuously, I can't predict if it will break when I hammer it again or not. This tragedy became her breaking point. And, this was the second breaking point of her we saw. The first breaking point was breaking point of her moral grounds when she accepted the ONS offer. This time, it was breaking point of her optimism and hope from destiny.
One logic, which supports this is to do a simple comparison. During the two years period of Aarav's treatment :
1. She had hope because a treatment could completely cure Aarav. This is the biggest point because if after treatment Aarav would have been still ailing then, what was the point of even trying.
2. Constant consoling by Rewa and others. Her family was not there for her.
3. Aarav still had that magic which made Katha overcome the pain of losing her love - Adi.
In this 5 months period :
1. No hope or treatment can revert or change the truth which came in public.
2. Her family was not there for her yet again neither Viaan was there, Neerja gone, Rewa gone, guni maa is not the best.
3. She was on verge of losing a perfect child, her magic this time to mental trauma. Also, if Aarav was behaving like that, there is no doubt he would have tried to inflict self harm. There are a lot of possibilities. Also, her love Viaan was gone for a long time and she was unable to do anything to get him out.
Unlike last time, where her optimism paid off, not in the nicest way but, her optimism paid off and Aarav was saved. This time, all her optimism and hopes were shattered in most brutal way possible. Out of nowhere dark night which was barely mentioned came out at the end moment and it shattered everything. Her being pessimistic and irrational and her character assassination makes sense. Her decisions, although wrong, feel human and realistic no matter how you see it.