I found the problem. The user started out as an admin but switched her group to something lower. I have a single JCE defautl profile set up for admins, and she kept the JCE editor setting when she switched. The default editor for everyone else is None, and when I switched her to that, she could edit her blogs again.
So the odd thing is why JCE would fail for her user level - it simply doesn't load ( no buttons, etc ) I suspect a recent JCE update caused this. It still loads fine for admins.