Bridesmaid Issue

She would not be my bridesmaid

Honestly, when I read your post I thought "thank you, next!". I would 100% cut her if this is the kind of "support" she is going to provide to you leading up to your wedding. I can't believe the way she acted in your other friend's wedding and 100% agree that you do not need that drama on your wedding day.

I would talk to her roommate first and express your concerns. If you're worried about coming across as a "tattle tale", I would say something like, "I wanted to reach out to you to see if you think that I am being too demanding with my expectations for the bridal party. X has expressed some concerns and I wanted to get your input as I value your opinion". Or something like that.

You need to have a talk with her ASAP. She's being both selfish and childish. If any of my bridesmaids (who were all also 30+, two of whom were 40+) had acted this way, I would have given them the boot early on. If you're worried to go directly to her, then first I would speak with the other bridesmaids who's her roommate. Find out if she acts this way with everything in life, not just weddings. I also can't help this feeling that if she behaved this way at another wedding she was, then maybe she's carrying some "always the bridesmaid" bitterness. Not that that excuses her behavior in any way. I just know that something needs to be said soon, as it appears you're only two months out from your wedding. One way or another, you need to tell her to either get her act together and act like a grownup, or get out. Maybe even start thinking about anyone who could be a backup bridesmaid if need be. Good luck.

Any attempt you make to kick her out of the wedding party will invite drama. You asked her to participate, and you're kind of stuck with that decision. Technically all she needs to do is get a dress and show up. She's not obligated to help with planning.

"Thus far every request I've made for help she's said she's unable to do unless it's done on her terms and schedule" --I would think this is normal? Of course she wants to help but on her terms, it's not her wedding.

Yes I'm planning to try to be as calm and polite as possible. My other concern with this is she's unlikely to react positively which concerns me about her attending the wedding at all. I feel like her attitude would likely be unpleasant if she attends as a guest. However, I'm not sure how to be just as polite about asking her to not attend at all.

Well as I mentioned her not helping isn't the primary issue. Her attitude and rudeness toward my MOH, toward another friend at their wedding and unwillingness to participate in reception events because of her concern with photos, is the main issue. The unwillingness to help is just the final straw.
And to be clear one of the "requests" I made of them was for all of the bridesmaids to stay in the same hotel (I intentionally chose one that's reasonably priced, but nice). All of them agreed to this and then last week she up and changed her mind and decided to stay elsewhere and dragged the other bridesmaid along with her. I don't think that would classify as "normal"

Her behavior has made it clear there will be drama either way. The decision is between dealing with drama for the next 2 months and the day of as a result of her presence or dealing with whatever potential social fallout comes from asking her to step aside.

I've already asked her to talk tomorrow which in and of itself was difficult to nail down and resulted in her launching into a speech about her schedule and how busy she is. A speech I've endured at least 3 times in the last 2 weeks.
So the other bridesmaid has known her longer and has occasionally made little complaints about her being selfish. However, the other bridesmaid has been known to overreact to things and between that and chalking it up to normal roommate spats and the fact I had not seen in personally I brushed it off. I will say in hindsight this bridesmaid has always done a LOT of complaining about how other people "pick fights with" or "attack" her for no reason. She paints herself as the considerate, soft-spoken victim and because I'd never met any of the people she was ever talking about (like I said I keep my group of friends very small) I just took her word for it.
So to sum up, I don't think this behavior is new. This means if I tried to ask her to be a little less selfish (in nicer words of course) she would not be likely to respond well.
I do already have a replacement in mind, fortunately. Though I also don't care too much about even numbers so just cutting her out without a replacement wouldn't be a problem to me

Oh I don't think I clarified on this. I have no desire to maintain the friendship. She had done a few things a few months ago (unrelated to the wedding) that made it clear she was not someone I had any desire to associate with. I had already decided I wouldn't speak to her once the wedding was over anyway. I only bit my tongue and kept her in to avoid drama and because she hadn't done anything that directly affected my wedding at that point. However now her behavior is affecting my wedding and stress both on myself and MOH.

So maintaining this friendship isn't a concern. Only the friendship of the other bridesmaid she lives with is a concern for me.

Just wondering how you "kindly cut her out"? How do you see that going?

It was actually a question/quote for Heather, because I'm just not sure how you kindly cut someone out. I wasn't trying to be condescending to you at all, and the question was not directed at you. You have misread my post.

Please re-read the quote in my post.