Kangana is probably sensitive to rejection, setbacks and criticism.
She never really got credit or hype for her talent or good films.
That and childhood trauma or expectations from self or bad experiences at hands of others seem to have made her bitter.
Not all people cope well.
People get angry or bitter or become violent or even quit it all and withdraw from world altogether or commit suicide.
It is never as simple. Sometimes people also get fixated with certain persons or incidents and try to prove themselves to them or want to get even with ones who hurt them. Or feel they need to prove they were right and others were wrong.
Especially being hurt at a young age can really mess up a person for life and I bet Kangana's issues are not just due to Hrithik. HR was just a trigger or final nail for already underlying self esteem issues she had or sense of bitterness or unfairness she felt.
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