Thinking about it scientifically, the part of your brain that controls love also controls hate, so when you love someone and they do something that you dislike or even are slightly offended by, even if it's a joke, the sensors in your brain go crazy and you feel intense hate instead of love. Also, if it is a romantic relationship, that same part of the brain is sent in turmoil because for the first 18 months, it is getting used to this interest in that person.
Well this might be dumb advise but its from a real mans man lol. i had a gf. and she cheated on me 3 times within 2 months, and we dated for two years. i never knew her slutty side at allllllll. and sry but even after that like i broke up with her, but i still loved her!/ hated her! Its hard to contol the emotions but you will get over it