From the Model Mayhem FAQ:

How can I find the friends I added recently? Why aren't they appearing in my Friends in My Stuff?
There has been a bit of confusion about what sorting by "Recently Added" means when visiting Friends in My Stuff.

In this section of My Stuff, "Recently Added" sorts your friends by the date they were accepted on Model Mayhem which might not be the behavior you're expecting!

If you're looking to find the friends who have accepted your requests most recently, you can go to your public friend's list via your profile page. Sort this list by "New-Old" and you should see the friends who have accepted your request or whose request you have accepted most recently.

Viola! You have two different ways to sort your friends!