I personally dislike the attempt to indict Instagram.
I agree, I didn't see it as anything other than a way she projected what she thought was expected of her. No different than wearing clean clothes and putting on a smile. Not once did I feel like social media was being portrayed as a "bad guy."
It seemed to me as if social media and the expectations that it creates in youth were brought in as potential factors. Of course, in reality, they may not have been - in order to make a sequence of jumbled events hang together in the, as you've observed, forced narrative structure, it's important to identify certain threads which can be used to tie the story together. Instagram and social media was clearly highlighted as one of those uniting lines. Villain? No. Let's not be so absolute.