That is odd, I could get the first idle_rear to work, but not the second. 
No matter what I did, it just skipped it.
Using an & and then a pause for the same length is a kinda strange way to do it though (I can say that 'cause I do the same all the time lmao).
I don’t know why it’s not working the way you have it, but I do know that you can make it work by doing this:
@TEENAGE MARIE walks to spot 0.822 182 240 in 3 AND TEENAGE MARIE is walk_neutral_rear AND TEENAGE MARIE faces right THEN TEENAGE MARIE is idle_rear
@pause for 2
^ You might have to edit the length of the pause, because “idle_rear” has its own animation time of roughly 1 second. 