How would she know you mentioned something to her father? If he tells her, it would be better to compartmentalize to yourself. It's set up to be a drama triangle in which there are no winners (except your daughter who can keep thinking she is a victim of persecution).
Our Dysfunctional Roles with OthersRead our feature article
here:
You're worried about your daughter, and obviously hurt by her, and also your grandchild. Stepping back from the drama, driven by the uncontrollable emotions of a pwBPD (person with BPD) is the first stage in reducing conflict, a first goal.
Do you see yourself getting drawn into the drama triangle? I'm not judging you here, all of us have stepped into it. The key is rising above it. And not all triangulation is bad, if you look at the link to the feature article).
You might want to start looking at the info to the right of the board, the communication tools and lesson 1 (to start... .I know it's a lot of info, but senior members here can help support and guide you). This is strategery.
To drill down tactically, what kinds of things set her off to engage in rages?