I understand that not everybody likes everyone else.
The part I don't understand is the one-way view that the person has, as if it doesn't occur to her that the other person could dislike her back.
In addition, I don't understand why dislike of a person should serve as an excuse for treating someone badly.
I really don't care if someone doesn't like me. I think that the only people on the planet who you need to like are friends and romantic partners. You voluntarily put them in your life. All other human relations and interactions do not require that you LIKE the other person. Civility is required in all interactions; liking the other party is irrelevant.