What Action do I take?

[Cadet]

She has said all along that she loves me and wants to be with me. She has said she knows what she is doing is wrong but can't stop.

Don't believe anything she SAYS and half of what she DOES.

I am a completely different person that I was when this started.
I am strong enough to end it.
She knows I have plans in place to move on without her.

Of course this scares her and so she lies to you to keep you as PLAN B.

She must live with her consequences.

YES - get some popcorn and watch her movie.
It might be a horror show but you can not change it or fix it.
She must do that.