I think we, as in the whole of fandom is being rather harsh on Bella. I know for the fact that I have judged her too harshly far too many times. Although I was by no means happy with the way she let Yuvi/Vik damage her reputation in front of the family, I think other aspects she can be excused.
She was a bit suspicious of the way Vik came and she blamed him for not reaching out to her soon enough.
She did not fall for his Mahir killed naagrani ma crap.
She did not fall for the Mahir set you up for molestation crap.
Although she had nothing but hatred for Mahir, she did not fail to notice that he is good human being. Remember that scene where the whole family was shifting to Sumi ma's mother's house? As she was packing she was thinking about all that Mahir has done.I distinctly remember her thinking that just because he did a couple of good deeds, that doesn't make him a good person. Despite her hatred she noticed his good deeds.
She did not let her best friend and ex-lover manipulate her into killing Mahir. Especially after Vik's return. She refused to kill him as she believed him to innocent. She could have been easily swayed if she had been stupid.
Although she did not know the rules of Naaglok, she acted with great brains when the time came. And it can be excused that she thought that those dreams were nothing but dreams only. She saw her mother die in front of her eyes. She had no hopes of ever meeting her mother. And with N ma being so cryptic, she thought the dreams were simply a reflection of her fears.
She seems well aware of her strengths and weaknesses. She knew of her weakness during the skin change phase, and so she wore the trishul to prevent anything wrong from happening. She knew right from the beginning that Vik would do something o trap her. That's seriously smart.
Bella is shown to be a Naagin with a heart, unlike Vish. She thinks things through before acting on it. So during the thinking process she appears dumb and weak. But she is a true and just ruler. Let hundred criminals go unpunished but one innocent should not get punished. I am sure she will come out of this one too. Let's just give some time.
Let's cut the girl some slack guys. She is going through a lot. I know for the fact that we all love her and that's why we are a bit harsh on her character but at the end of the day it's the cvs who get to have the last laugh. So far her character graph has been quite a consistent one. Let's hope it stays that way.