<human>: Can you condense the text into three sentences or less?

Background: They have been dating for over 2 years. They spend everyday together, nearly codependent, and don't have friends outside each other. They talk about marriage and family and moving away to New York in the future. They are moving in together in a few months. 

Story: I was on Instagram and came across the boyfriend's profile (Note: Roommate does not have an Instagram). I clicked on a girl's profile that had liked a bunch of his pictures, and I knew I had mutual friends with her. Well I look at her pictures and there are several screenshots of messages he has sent her. 1st message I see: "I've been thinking of you and I wanted to let you know that I love and miss you and you are one of the coolest people I know."
Woah there, that doesn't seem very appropriate to me. I dig deeper, and I see another screenshot of a text sent 4 days after their 2 year anniversary in the summer. It says pretty much the same thing. A few days later, this girl posts a screenshot of their "skype date," and a caption of how much she loves and misses him. Girlfriend does not know about this skype date, because he suspiciously decided to not stay over with her that night. And it turns out, my roommate had complained to me last year about her boyfriend driving six hours away to go visit this girl. My other roommates took it upon themselves to tell her, but she is now mad at everyone, believes his lies, and refuses to look at the pictures. Is this considered emotional cheating? And if it is, should I do something about it?
<bot>: I found screen caps of inappropriate messages on some random girl's Instagram, sent by my roommate's boyfriend. She refuses to believe the pictures exist. Is this cheating? Should I do something?