Bridesmaid won't buy her dress and the window of opportunity is closing. Sos!

I've had a long engagement-- we've been engaged for over 2 years. My bridesmaids accepted their roles a month after I was engaged. So they've been "bridesmaids" for almost 2 years. It took me awhile to plan our May 2020 wedding with a lot of bumps on the road.
In May of this year, I set a date for all of my bridesmaids to go to David's Bridal to choose their dresses. They're all to choose their own dress in the color Dusty Sage. Unfortunately, a lot of the bridesmaids had things pop up last minute, so we rescheduled for August. I told the bridesmaids to have their dresses ordered absolutely no later than September 1st. Which most of them did.

One of my bridesmaids, who happens to be my best and closest friend, is being a little (a lot) problematic. When we went to David's Bridal in August, she was the only bridesmaid that wasn't there. And to make matters worse, she had slept over my house the night before. She was literally with me THAT morning. And she didn't go because she was too hungover. Whatever, I begrudgingly let it slide. I just reminded her that the dress needs to be purchased by September as it takes months and months for dresses to come in.
She never purchased her dress. I have followed up with her time and time again. She gets emotional and claims she is just having trouble getting the money and promising she'll go to David's Bridal that weekend, and never does. Here's where I'm getting agitated... I have seen her spend her money on concerts, conventions, and liquor. I hear her talk about how she pours money into a game app on her phone. I've seen her just generally spending money on all these different things. And it's really frustrating for me to see her piss her money away when her bridesmaid dress still hasn't been purchased. She just resorts to tears when she's asked about it or offered solutions or budgeting assistance. She lives with her parents still, so she's not paying rent or utilities. She does pay her parents' phone bill as well as her own, and has car payments and student loans. But half of her monthly income I can't even allocate where the hell it's going. I don't understand how she has no money?! I have even given her some reward money I've won from a contest but she can't buy a stupid dress???We're pretty much at the end of the line and she's about to miss her window of opportunity to buy the dress. Because David's Bridal is currently estimating bridesmaid dresses to be shipped in around late March and my wedding is in May. I don't know what to do. I've texted her so many times. And just this morning, I've texted her and told her QuadPay could be a great option for her so she can make the purchase now and pay over the next 2 months without interest. But of course she isn't texting me back. And if she does, she'll just tell me how stressed she is about money, but how she PROMISES she'll go this weekend. But she won't, I'd stake my life on that.I'm not a confronational person and I hate putting my foot down with things. Especially with her as she doesn't take any criticism on any level very well. I can't imagine my best friend not standing up there with me as a bridesmaid. But we're almost at that point and this would definitely be damaging to our relationship. She's been completely irresponsible and I've seen repeatedly where her priorities are and it sure as hell isn't this wedding. I don't even want this wedding to be the center of anyone's universe, but she isn't even trying at all whatsoever and it's honestly a slap to the face. As a bride, I have other things I should be worried about and a half-ass bridesmaid shouldn't be one of them. Okay sorry, rant over. I just expected so much more from my best friend. She's not even meeting the bare minimum expectations and honestly it's starting to ruin this experience for me. I cant afford to front the money for a dress for her and wouldn't trust her to pay me back if I did. I also don't want her to not be in my wedding so I'm really torn on what to do here. Any advice you guys have would be so appreciated!