I have to say, since I've been seeing this comment a LOT, and because I boarded this scene; This was not fan service. She simply stayed in this position because she didn't NEED to turn around. The reason I didn't have her turn was because she wasn't taking Pinkie seriously. It's a physical visual element to help show how not concerned she was about the situation. This type of action is consciously thought out in the storyboard process.
Psh, I dunno! XD You shouldn't have to worry at all about drawing them from behind too much. From my point of view, nothing about it draws any attention. But it's a strange world we live in. Just keep doing what you're doing. Your guys' work is phenomenal and we love it to pieces. ^^