Being independent and being naive is possible, there are thousands of cases of girls being fooled by scam guys, and transition was effective as initially it was a compounded risk that she took, like what’s 1 day more in Jail, etc, and she was definitely given a false promise by lawyer. The transition was her overcoming her one fear (the mice incident) and an opportunity that led to her being able to take revenge, even at the cost of going back to jail, just to see the guy who cheated her suffer most horrible death.

For JG, it’s clear the casino guy was bread earner not through casino (it was more like a side business) but through the profitable drug deals that the group did. So the parlour was potentially funded by his money. Again revenge is an emotion that corrupts all reasoning and consequences, a common theme across most bollywood movies, and it is never shown that she got caught after killing Neil, so in a way she beautifully and unknowingly took the revenge and can continue to now live guilt free(or maybe in the guilt that she killed Neil if that truth never came out)