First of all it's not wise to have too much time between the time a Rishta is finalized and Anand Karaj.
Secondly, there is no concept of having any sort of special relationship unless the couple is married. The relationship should be normal relationship that all Gursikhs have with each other i.e that of siblings but in this case, the contact should be minimized because of obvious reasons.
Most of the ones who do keep contact, end up making mistakes. Even if they don't make mistakes, they become very close emotionally and in the event this Anand Karaj does not take place for whatever reason, it can have a devastating effect on the couple.
A Gursikh should always be careful that none of his or her actions should stain the White chador of Sikhi.
Kulbir Singh