Order of friends names in Facebook chat?

[Saywhat]

I recently accepted this person's Facebook friend request, since then every time she goes online her name always appears on top of the list of my online Facebook friends. If not on the very top of the list, she on the upper part before the "More friends" section. Does Facebook have a particular way on arranging names of my online friends on the Facebook chat? Like for example the last person I message to appears on the very top, something like that. I'm just curious.

BTW:
I have never message or chat that girl who always appears on the top or the upper part.

[Specter Boy]

It depends on how much interactions you have between your friends and how recent they are, there are some other factors about this, Facebook uses some complicated algorithms.