Because you separated each of your CREATE statements by an ";" each statement becomes their own transaction and are not related to each other. In other words, the variables created in the prior statements cannot be used in later statements. If you remove the ";" and put the relationship creation with the node creations then you will get what you are wanting. The following is an example.

CREATE (a:user {...})

CREATE (b:user {...})

CREATE (a)-[:Friendship]->(b)

A better place to put this type of question is in https://community.neo4j.com/