I am sorry to hear of this for you and your daughter...sadly a pattern has been set for her since she was young and has come to live her life in this narcissistic manner and when things don't go her way she wants to leave and fine something better. The difficulty becomes getting her to see that these patterns are destructive to those around her and many attempts to get her to see this are met with anger and a refusal to look inward....
so what to do???? When things feel calm I would sit with her and let her know how you care and love her but feel that some of these patterns are not healthy for you and her daughter and hope that she would be open to speaking with a professional to look at her feelings so that you can all live in harmony as a family.
I don't believe you have an easy path here so responding to her with love and empathy is your best chance to get her to see...over time.
As best you can encourage her to see someone while being empathic to what she must feel inside with so much pressure she puts on herself and by extension you and your daughter.
I await your thoughts.
Can I support you further?
I am in EST in the US and will be signing off for the night soon so if you respond after that, I will be sure to respond back in the morning my time. Please let me know if you need further support as I am happy to continue. If not and all good for now, please offer a positive rating...either way, I am available to continue. Thanks.
I am available for the day now and am here when you are available.
I remember speaking to you here several years ago...we worked well together so I hope to hear back from you to go through this.