I'm not seeing anything at all suspicious or sinister about Mollie's social media use - not her retweets, not her Instagram or VSCO posts, not her Snapchat use. I'm a high school teacher and all of that is 100% in line with most of my students' social media use. The fact that she was trying to move her boyfriend back to the top of her list on Snapchat is pretty logical to me. She was living with him, his brother, and his brother's fiancee, whereas her friends from college were scattered about for the summer, so it makes perfect sense that Mollie would be Snapchatting her "away" friends more often than a person she lives with. Your Snapchat "best friends" list shows the people you've Snapchatted with the most recently, so if she'd been talking with friends more than him, he automatically would have dropped down. I know that often the boyfriend/partner is guilty in these kinds of cases, but I'd be completely astonished if her boyfriend had anything to do with Mollie's disappearance.