It's not weird at all. This happens to everyone in all sorts of situations. (you see it a bunch at weddings in my experience)
This is a big deal for a friend and you went all in to help her. That's a great thing.
What happens though is that because you are helping her out with this, you start thinking of "her issues" as "our issues". You start inserting yourself emotionally and mentally into the situation. But you aren't really there. I don't mean this harshly at all, but it ain't your kid and it ain't your life. You can help her out with her issues, but you gotta remember they are her issues, not yours and not both of yours.
And sometimes to do that, you just gotta take a breather from the situation.
And yeah, for that last stuff, you've got every right to freak out about that shit a little. It's your choice how deeply involved in this you get and that is both alot of responsibility and the kind of thing that'll suck you right in to the heart of this whole situation. And all that without any sort of clout to back up that connection, if you get my drift. (ie - you may think you are really involved, but when push comes to shove "it's my kid" basically shuts you out of major decisions)