If the person you have a crush on left you for another person, then it's normal to hate that other person.
If you developed your crush on a person who was already in a relationship with another person, then hating that other person just seems weird to me.
_________________
The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.