If someone wants to control you then they will want to control you right down to your very thoughts. In other words then, the last thing they are going to want is your friends talking in your ear and potentially persuading you that this person is bad news. For that reason you might then find that they subtly try to isolate you from your friends. They might do this by offering you better alternatives at first such as luxurious dates, but timing them so that they coincide with when you would otherwise have been doing something with your friends (if they knew you had prior arrangements already then question their motives). Likewise if they hear anything bad about your friends then they will be quick to jump on it and make your friends out to be worse as a result. Saying ‘I never liked her/him’ or ‘You don’t need friends like that’, as opposed to the normal response which would be ‘I’m sure they didn’t mean it’ or ‘Give them time, they’ll come around’. You may also find that they answer the phone and make it difficult for you to speak to your friends, and this can even be scary in extreme cases. If ever they say that the only person you need is them, then start to question things rapidly. Emphasize to them the importance of independence and of being your own people as well.