How should I offer a compassionate ear to my mother while setting healthy boundaries?

I hope you are all well. I have been studying Buddhism for a few months and I am very grateful for the teachings. I've visited this website frequently for similar questions and this is the first time I am reaching out to this community. Since bringing Buddhist practices into my life, my relationships have improved, especially with my mother. However, I am finding it difficult to navigate what would be the most helpful or skilful actions for myself and my mother during the suffering she is experiencing at the moment. A bit of background on my mother: she has narcissistic tendencies and since my childhood, has leaned on my siblings and I for her emotional needs especially in times of suffering. I am now 20 years old and the relationship we share I feel is much healthier than even a year ago, as I struggled to understand my own suffering and suffering of others before I began studying Buddhism. My mother is in the midst of a break up with her ex-fiancé and I am the only one she has shared this with in our family unit (I live with her and my younger sibling who is 17 years old). While sharing with me her feelings about this and having my shoulder to lean on, she began sharing things she dislikes about my father and his family (ex-fiancé and my father are different people). I understand the importance of boundaries and I am not sure how to lend a compassionate ear for her during this time while communicating that I cannot be a therapist for her. I recognise that everyone is in care of their own suffering and that it is not your responsibility to alleviate the suffering of someone else, only they can do that. I would like to share compassion with her in a healthy way for both of us as our past had no boundaries, and I had felt that her emotions were my responsibility. In other words, I want to do what I can to support her during her suffering in the most healthy and skilful way for both of us. How would one go about this? I appreciate all comments and advice and I'm happy to go into more detail if you would like. Thanks for reading.