Unreliable

The people they flake on aren't as important to them

This is a somewhat harsh truth. If someone's made plans with a friend or group of friends who aren't particularly important to them, they won't lose much sleep over flaking on them if they get a better offer or decide they no longer feel like going. This isn't to say the flaker completely hates their less important friends, it's more that they view them as people they'll hang around on their own terms and when it's convenient for them. If it suddenly becomes inconvenient, they'll pull out.

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