How do you deal with flaky friends?

A month in advance, my friend RSVP to my game night event saying that she will be there. I sent out the confirmation emails two weeks later and she says she can't make it and that she has a holiday concert she is attending that same day that she already said she would be available for. We also spoke on the phone the day before and she didn't mention this even though I said "I'll see you soon."

Do you think she was flaking? I have been seeing a lot of discourse on Tiktok about being a good friend and it has me wondering. In college, she would flake often and has expressed rekindling a friendship now that we are some years out of college. I'm a bit on guard when it comes to her because I can't stand a flake.

Do you think she was flaking? How do you deal with flaky friends?