I am debating about whether to ask one of my childhood friends to be a BM. We were very close in high school and have kept in touch ever since. Like, practically sisters close. We did everything together and I have always envisioned her as a BM. As friends do, we've drifted apart a little over the years. Lately we haven't seen a lot of each other, even though we live in the same city. It's always me contacting her, never the other way around, and she mostly declines my invites to meet up, or says she has to reschedule but then never does. She is generally sort of flaky, frequently extremely late for things, or will back out at the last minute. She's always been this way and I don't expect her to change anytime soon.
However, it's gotten worse lately and I'm worried it's actually personal now. She declined her invite to my engagement party, but didn't tell me why even when I asked her (gently, I think): she just said she had a "prior commitment." Later I saw she'd been checked in on Facebook at 2am at a bar with her friends. I have tried to give her the benefit of the doubt-- maybe she had a medical procedure or something family-related, and just went out later as an impromptu thing. But I have an evil voice in my brain that says maybe she just doesn't want to be my friend anymore.
We finally got together for the first time in several months and had a great time. I really enjoyed spending that time with her and she seemed to be having fun. After that experience, I decided to go ahead and ask her to be a BM. I recently texted her to ask when is a good time to give you a call, nothing bad

. Several days later she still hasn't responded to my text. In the meantime, she was silent on a couple of Facebook invites as well.
I have seen a lot of brides posting on here about BMs who drop off the face of the earth and acting annoyed about it. I think my concern is less that she won't be around to help plan/DIY, because I don't expect BMs to do that. I'm just actually worried that I will ask her to be a BM now, and by the time the wedding rolls around it will be awkward because we have drifted farther apart by then (hopefully not). But she's very sensitive, and we have such a long friendship, that I'm also afraid she will be offended if she isn't asked. For all I know, she's offended she hasn't been asked yet and that's why she's acting weird. Any thoughts?
"I'm not a rude bitch. I'm ten rude bitches in a large coat."