From what I get from your post, it sounds like they had an awful argument, and there might be something huge going on.
In that situation she'd be in pain, and maybe really worried about things. Love pain is hard. To then be talking with your best friend about her wedding would be even harder.
I think she told you several times that she couldn't talk about this right now. Remember, as a bride your entire thought process is on your wedding - there's a reason we are called 'bridezillas', as our wedding things become insanely inwardly focussed at times.
I know you were waiting from before to find out about his coming to the wedding, but maybe there's something more going on there with him. Give her the benefit of the doubt here, and realize that you're not exactly there for her right now - understandable with your wedding so close, but do give her a break. She still has life things to deal with.
I would just gently say to her look, I don't know what's happening with you both and I'll be here for you, but right now I have to have this wedding thing settled. Since your bf can't confirm being able to come, I'm inviting my uncle instead.
Leave it at that, and remember that our emotions all run a little high at times. Especially with a week to go before your wedding (yay, how exciting!
) Let go of your anger and concentrate on your friendship with her instead. Don't even mention the bf unless she does.
And most of all, enjoy the last bits of planning before the day with your husband. Get plenty of sleep and avoid all the stress you can.