Honestly, it really isn’t that different that if she were still alive. Relationships aren’t so much a single bidirectional thing as much as two strongly correlated unidirectional pieces. By that I mean that there is both how she relates to her grandmother and how her grandmother relates to her. Even if her grandmother were alive, the only part she can directly affect is how she relates to her grandmother and that doesn’t change now that she’s dead either. Of course, typically by changing how one relates to the other that often has an indirect effect on the other part of the relationship, because by treating her differently she’ll likely end up relating back differently.
Getting a bit off point there, but one absolutely can do work on relationships with people that one either no longer has contact with or are dead and it doesn’t necessitate invoking any sort of metaphysical stuff. Experience through the grief and at the end forgive and/or apologize as necessary, then let go.
In fact, on that end apologies and forgiveness are also the same sort of thing, in that they often go together, but an apology can be given and forgiveness returned or not and the same for forgiveness given with or without an apology. It is all about creating a state of grace in that aspect of the relationship that you can control.
So, specifically to that end, she may feel you need to apologize to her for her getting involved in that drama or her not getting the whole story or for how she treated her as part of it, I can’t really say. Anything that one feels that did that they shouldn’t have or didn’t do that they should have likely deserves an apology whether or not the other person may or many not have felt wronged. Similarly, she may feel she needs to forgive her for how she reacted to the drama, for her not being straightforward about her involvement, or for how she handled the inheritance. And so, also, one should forgive for anything they feel wronged about whether or not the other person actually did something wrong or not.
Anyway, I guess my whole point is just that, really, talking to someone seems to make things easier, it can give perspective and make it easier to apologize or forgive and experience grief, but ultimately those steps can be taken with or without the participation of the other person. In fact, somtimes it’s easier without the other person, particularly if that person is still behaving beligerently.
Either way, she’ll get through it, and it will get easier in time as well.