As you grow gradually, there are many things yet to learn. And inculcate into your practices. There is also the matter of culture to take into considération. It is not easy for a Westerner to understand advice from an Easterner and vice versa - our ways of life are very different.
Buddhism is a path to discover the self. You can not change others, only yourself.. In discovering your self, you light one more candle in the darkness of the world. In other words, you bring light to the darkness around you.
This involves many things.
First, your mother is who she is, and you cannot change her. A seed grows into a tree, and not the other way around. Your mother is a tree, she can not be un-grown, just because you would want her to change. This means, you will have to accept her. Without hating her or using labels on her. Where there is anger or hatred or judgement of others, or calling others names (like narcissist), Buddhism teaches us to look at the source of that anger - within ourselves.
While you hate (or dislike) someone, you can not love them or have compassion for them, and it will tear you apart to be kind to them.
A buddhist practice to learn then, is how do we deal with our anger? Our hatred? How do we deal with our need to judge others??? How do we let go of our hurt? Do we want to...?
2.) Suffering. Buddha teaches us that to live is to suffer. Life is suffering. In other words, you can not take away anyone's suffering. Not even yours.
But you can help others. Not with pride or hatred or drawing boundaries out of self preservation, but with humility and service.
A good first step is to practice forgiveness. Forgiveness for her, and forgiveness for you. When you achieve this she will not be able to hurt you anymore. In any way. And then the door of compassion and kindness will open...
Another good step is to banish hurtful words from your vocabulary. Like "narcissistic". Thoughts are very powerful things. And our words are a product of our thoughts. Cleaning up our words/language has a profound effect on the inner us...
While you have not forgiven her (or yourself), while you feel she is a narcissist, while you can not yet stoop low in humility (service), letting go of pride and hurt, you can not really alleviate her suffering in any meaningful way.
In setting foot upon the path of Buddhism, one is supposedly setting foot on the path of releasing the vices, and embracing virtues.
Setting boundaries is a quick-fix bandaid.. Yes, the wall will keep unwanted influences out, but it will also keep all the nasty things in, and perhaps push them in deeper into our psyche. Buddhists believe in reincarnation... Why build a wall and build the shit up, life after life...?