Got to catch up on your thread...everything is beautiful! You are so organized. Sorry to hear about the bridesmaid drama. Unfortunately, as @veryvalentine mentioned, it is really common at this point in the wedding planning process. It stinks. I wish I knew why weddings bring out the worst in some people but they truly do. I no longer associate with a "friend" of many years because of a situation similar to yours so I can relate. Ultimately though, I can't say that I missed her on the big day. She hadn't been the most supportive to begin with and I felt like for many years, I was keeping the friendship together simply for the sake of the amount of time we had been friends. Look at it this way, on your big day you really want to be surrounded by people who LOVE you and your husband to be AND these are the people who are going to be there to support your marriage in the years to come. You don't want to feel like you forced anyone or that there might be any jealousy/spite/malicious feelings surrounding your big day. You will want those with the truest of intentions beside you and sadly, that might not include your friend.
I am sure you are under loads of stress and this is probably just about the last thing you need but I would give it some time. You have more important things to do at this point. I would eventually get around to asking her for a definite yes or no when you are ready. I say when you are ready lol because, just my opinion, I wouldn't even acknowledge her bad behavior with the response she is looking for. She is expecting you to be upset most likely. It will totally confuse her if you calmly ask, when you are ready, if she has made a decision about attending the wedding so you can make arrangements. Hopefully she will do good by you but if not, she misses out. The beauty of DWs is that it is not just a one day thing. It is a bonding experience, a memory that will last a lifetime. Those who are there for you and your husband to be will develop a stronger bond with you both. If she chooses to cut herself out of that equation, you will have a definite answer regarding your friendship, if nothing else.
Sorry for the novel but it makes me so sad to see other brides go through stress and anxiety over bridal party drama. It will all work out for the best.