The best thing you can do is leave her completely alone. Do not engage her about ANYHING that your kid.
No small talk. No "how ya doin?"... Nothing.
Starting right now, and going for an undetermined period of time, you don't care how's shes doin'... And you don't need for her to know how you're doin' either... Cause you're doin' fine my man, just fine.
And that's how you act.
No matter how horrible you feel inside or how much you miss her, you are fine. You aren't going to die from this... This is just for now. Things change. Things ALWAYS change. You can't predict HOW... But I promise you, this phase you're going into won't last very long in comparison to your entire life.
Things WILL change... And when they do you deal with it then.