When I got engaged about 2 months ago, I told my old college friend that I was about 99% sure that I'd ask her to be in the wedding party. I had planned on giving her very little responsibility other than wearing a particular dress and letting her help plan the shower/bachelorette parties (she said that even if she's not in my wedding, she wants to help plan) because she is very flaky and unreliable (she is never less than 45 minutes late for anything). I would normally be okay with this because I'm used to it and am willing to work around it, since she lives an hour away and probably wouldn't be able to make it down as often anyway.
However, over the last month or so, she's been behaving way more erratically, irrationally, and irresponsibly than usual. Instead of going out drinking and partying heavily every weekend, she's now going out several nights a week. The last few times I've seen her or planned on seeing her, she's either been high, hungover, or she doesn't show up at all. I'm not even going to start talking about her relationship and body/eating issues. Last week, she supposedly "unfriended" a mutual friend of ours on facebook over a debate about feminism. She doesn't answer our calls/texts for days (or at all) and says we're overbearing when we call her out on her unhealthy behavior. She takes no accountability for her behavior and gives nothing but excuses.
I'm really worried about her and hate to see her going down what seems to be a really destructive path. But she doesn't feel like she's doing anything harmful and won't seek help or even slow down. So on top of all that, I'm nervous about asking her to be a bridesmaid because I doubt that I can count on her for anything if I were to ask her. I still want to invite her and even include her some way if possible, but I’m pretty hesitant to ask her to stand by me when she can barely stand (figuratively and sometimes literally) on her own.