Shri, you raise a lot of very good points and I'm sure I missed out on a lot of discussion during the week when I wasn't around this forum...I'm going to go off on a tangent now, just writing out thoughts as they come to me...
I agree that things could have been done in a different way regarding Sameer's character, but now that they've turned him into a very murky character, I don't know what else to do except sit back and watch the proceedings. Maybe there is a reason for all of these characters like Radhe, Inder Sharma, and Sameer Diwan being portrayed in such a way...Maybe it's just a way to tilt the scales in Ricky's favor...I don't know. Somewhere in all of this, I'm guessing that the ones motivated by monetary gain (Sameer, Inder, Radhe) have been depicted this way to show that. Greed as a base motive, in contrast with the few characters who are happy with very little. It's frustrating to see that more and more people are turning out to be stacked in the former category, but there are more people like that anyway. Ricky may not care for money, but he has other flaws and drawbacks that make him real and not an idealized hero. At this point, I've learned to not get too involved in the "what-could-have-beens" because that list is always going to be endless due to our varying visions and expectations.
Even if Indira isn't consciously sitting and dwelling on the contrasting qualities of the two brothers, I still feel that to a small extent, she believes that Ricky would never overstep his limits the way Sameer did, and the small amount of time she has known Sameer was enough for her to assess his character. At least there has been consistency in her perception of him - his actions just reinforce that negative opinion she has of him more and more. And even if Indira isn't comparing the brothers, her instinctive reaction to Ricky getting hit with the rod was a major indicator of her feelings for him.
As for the regression from "Indira Sharma" to "Hitler Didi", I expected this to happen. Indira's trust has been shattered yet again by someone she never ever thought she could come to like, much less love...But she fell in love with him despite his "flaws" and accepted him after years of keeping a tight hold on her heart. She couldn't control the effect Ricky had on her...And to suddenly find out that the man she loves has hidden aspects of his life that she doesn't know about...who wouldn't feel angry? Indira is already known to be volatile (or at least I think she is volatile because of her vulnerability) and her excessively exaggerated actions and comments hit their mark in terms of intent for me personally. The way I see it, Indira has been conditioned by her experiences in such a way that she tends to react in extremes. With Vidit Bhaiyya, Ishaan (sometimes), Amma, and later Rishi, she was slowly starting to tend more toward "balanced" expression of emotions...But maybe this is the point. When her support system has been snatched from her, the stabilizing factors and comforts are gone...and coupled with frustration, grief, and anger, it's just too much to handle and it seems to the audience that she's out of character. I'm going to interpret this as a sort of relapse. An extreme relapse...but I can't ignore the little details that still hint at the "Indira Sharma" wanting to break free from the "Hitler Didi" inside of Indira.
*sigh* I doubt any of that made sense. Just trying to put my own views out here...It's not an easy task. As always, I greatly appreciate those who have taken the time to read my comments!