If you dream that you love someone that you hate in real life, it would mean that you have a secret crush on them and maybe you really do like them even though you say you hate them. Sometimes your subconscious knows what we really feel better than when your awake.
Maybe deep down you do like the person--otherwise, it would be a nightmare!!
It means that even though you might have a deep set hate for the person that subconsciously you long for their companionship and might even hate them because your jealous or because they don't want you the way you want them