u mite be right but it's not always that simple.
sometimes the girl goes to her sasural with thoughts of accepting her in-laws wholeheartedly.
While these in-laws may not be wicked or evil, they might be reserved or have this cunningness where no matter how good you are with them, they don't accept you wholeheartedly.
They may be sacchirinely sweet with you but you get the vibes that something is not right.
What's more important to them is that they have the upperhand, like the jethani or sasuma - ensuring that the control remains in their hands, despite the new bahu, the FIL who cares about his social standing in society even at expense of his or DIL's happiness.
Unfortunate but true...life is never fair, sometimes you have an understanding MIL but underdeserving DIL or vice versa.
Best for a woman to do is to stick to her principles, respect her in-laws (whether deserving or otherwise) and try to do the right thing in light of the situation she finds herself in.