"I really can't like her" = The person is not allowed to like her, because the verb can't implies they are not 'permitted' to. Or allowed. "I really can't be liking her" = is similar to the first sentence but obviously with a extra verb, "be". In this situation, the person is adding more emphasis on action. It just adds a variation, maybe a bit more emotion. This sentence is sort of not used often, you hear often 'I can't be seen liking her' etc. You could use the phrase but it seems a bit informal. "I really can't get to like her" = Still implies this person is not allowed to like 'her' but with emphasis on not being able to 'receive' the opportunity. ''I really can't come to like her" = Come is a verb that implies an advance, or movement forward so to speak. It can be used in a very physical sense or more philosophically. This is a very powerful sentence, because it implies you can not "move along/ move forward" with liking 'her'. The sentence is radically different from the other 3 because the other 3 implied the person was not ALLOWED to like 'her' but in this sentence the person can not on their own like 'her'. As if their is no chemistry. I hope I added some clarity.