Is there a word that describes a person who easily gives up on others

Example:

Person A had expectations of person B. After A gets to know B, person gives up on building a enriching relationship. A stops investing in the other person (i.e. stops giving feedback, stops trying to be understood or to understand). A presents a recurring pattern.

Solution 1:

If you are looking for an adjective, I would say that person is being apathetic.

From encyclopedia.com

showing or feeling no interest, enthusiasm, or concern.

Solution 2:

You could call Person A fickle.

From the Oxford Dictionary of English:

changing frequently, especially as regards one's loyalties or affections.