There are always going to be some people able to feign the signs of being in love with their partner, but their feelings of anything other than their own interests are all they have. The person with the feeling of love will do whatever they believe is necessary to continue the relationship, and they could be deeply hurt before they realize it is truly over. There might have been a time or two when they were willing to call off the relationship, but they remained because their partner was still claiming to love them.
When the time comes for the relationship to end, the person who has fallen in love often finds it untenable to make the choice to leave easily. They want one more chance to make it work, and they are seldom able to understand why the other person is willing to let go of them. They have not seen that love is only coming from their emotional investment in the relationship, and the other person has few or no real ties to them.
Giving up on someone who is loved can be the most difficult thing a person can do, but their partner may eventually force them into it. The partner’s lack of feelings towards them could turn to an active dislike or disgust if they cling, and they will eventually feel at least that emotional emanation. It could be the turning point that lets the two of them separate, but they will generally never be able to be friends when it ends this way.
It would be best if the two people could mutually choose to end their relationship and remain friends, but that seldom occurs in this type of situation. Many times it comes down to the one with the least emotional investment turning on the person in love with them, so they must force them to end it.