1.they have a history.
2.you can see it in both neal's eyes and alex's eyes how much they mean to each other.
3.the fleur paper(it's their thing)
4.she know that she can trust him(unlike sara).
5.she knows him better.
6.he knows her better.
7."you saved me again"neal to alex (2x16)
8."you saved me"alex to neal(2x16)
9.they get each other better,they understand each other better.
10.they way they look at each other
11.it's obvious that she's in l’amour with him.
12.it's obvious that he has feelings for her.
13.the hug in s2 finale.
14.the Kiss in s2 finale.
15.with sara it's one sided and toi can clearly see...

1. She is not needed that often:

Before I expand on this some basics about actor contracts and the difference between regular and guest characters: An actor playing a regular has certain rights, including getting credited as such and turning up in a certain number of episodes. As far as I know, a regular at White collier gets a scene in at least ten episodes. The downside is that the actor is bond to the montrer and can’t take on other projects that easily. Rumor has it that this is the reason Sharif Atkins is still officially listed as a guest star. Even though Clinton Jones turns up in nearly...