No one feels - even if they say so out of anger or frustration at Humeira's character - that she deserves being used and dumped.
She has been very stupid in believing Haider's "your dad doesn't like me; let's run away" without any thought. Haider is her Dad's business partner , young, unmarried - she could ask her Dad why he dislikes Haider. She has been stupid about trusting someone she should not. In fact, in this case, Haider did not even promise a lifetime of love / marriage.
But I completely agree that her crime (rather mistake) does not deserve this kind of punishment. But is always punishment proportionate to the crime? A young girl feels bored and goes out for a walk alone in an area / time that's not really safe. She gets assaulted / mugged / killed. Her mistake is too, too small and her punishment really big. Happens all the time.
About Haider, well his action is wrong and cannot be justified by anything including revenge. I don't believe that kids should suffer for parent's acts. But I don't think he's a pointless addition to the show - CVs needed to add something fresh to the stagnating story and they chose a good looking, charismatic actor in a morally ambiguous, interesting role. Ayan is more central to the main plot but CVs never ever gave his character the kind of prominence needed. And made the tale of 2 brothers very lop-sided. HaiRa or AyRa does not matter to me :)