Speaking from my experience with an ex wife who was probably narcissitic and what I read about it, I think both faces were real.

In the beginning of our relationship, my ex wife did have her manipulative side but she was genuinely loving and caring. She was fierce in how she protected me when I had a burn-out and later a depression.
When things first appeared to get better but I eventually relapsed, she turned and became my worst enemy.

My ex wife did not drink etc. but I believe this big shift in attitude is a clear parallel between our stories. You should keep in mind that narcissistic people can be very charming. Things go great as long is you fill in their need. In my opinion, both sides are the real her. But you should also realize that you won't get the old her back.

The way I deal with this, is that I try to cherish the memory of (most of) our first years together. If I would not try this, I would not dare to move on (not that I manage to move on, but I do have the desire).
On the other hand, I have enough damage to make sure I keep a safe distance (we do not have children, which makes things easier).