C.B.
Spell it out for her! Let her know that "Gosh if you're forgetting so much, maybe you aren't ready to go into first grade. I'll just have to call the school and let them know to keep you in kindergarten". Sometimes something like that will kickstart their engines and get them back on track.
Otherwise, you're stressing out too much over it. I would back off a little, being she's only 5. Kids go through phases. Don't set such high standards and expectations, because if they're going through a phase, that's what's important to them, not reaching everyone else's standards.