If I were her, I would consider this ghosting.
That last look on 3rd wheel's face is typical of a very jealous, sexual predator man who has determined to take someone else's woman by any means possible. This is such a clichéd storytelling development that is used by authors to stir NTR-like rage in the audience. A prime example of this is the series "Boku no Ie ni oide Wedding" which has a essentially identical plot line.
...one text in a month is okay with everyone? I have been contacted more by guys I wasn't going out with, so if a guy did that I was seeing, I don't know that might be a deal breaker for me! lol I get that he did warn her about this, but shame on him. I really do like him, but this behavior is just cruel.
I didn't like that last look from SL, but I think it was just to mess with our heads.