How do you pretend to be happy?

Yep so it's happened again. After losing 4 of my precious babies someone I know that probably shouldn't have kids is pregnant. And it's a situation where I have to see them all the time and pretend to be happy for them. Really you are so self involved, don't have your own place to live, barely have a job, and think of no one but yourself and never once have you ever said anything about my babies but you get to have one. I still have a hard time being ok with that. Yes I think we are at the point we may never have children but I still can't be truly happy for you. It is so hard to put on that happy face and look excited.