It sounds like you need help.

Sometimes therapists will make exceptions... In other words, they might schedule an extra appointment for someone who really needs it. So, have you tried that? Have you tried asking her for an "emergency" appointment? I would explain the cutting thing and tell her how serious it is.

Can you see a different therapist in the meantime? It's not really ideal, but it's better than nothing

If you think you're an immediate threat to yourself, I would go to the ER.