Do you think you got so upset because the friends were talking about her being with her new boyfriend, and that you were imagining her, him, and the two kids as a healthy little family, like it's something you could have had but lost?
My ex is probably with someone new but luckily I don't know about it. If I found out he was backpacking with some woman and her two kids, my ass would be kicked too; I'd be totally devastated. I think the biggest part of the pain would be realizing how little I actually meant to him. Do you think that is part of what happened with you? I mean, here you are suffering, posting on SR, and not even considering dating, and she is playing happy couple with some unsuspecting codie. It does really suck, Zen.
Any info you get about your ex is a form of contact in that it stirs up your emotions and makes you think about her. Maybe you could tell your friends not to say anything to you about her? The more she can vanish from your life, the better.