I can see why you think warning your grandmother would be a kind thing to do, and I can see why you thought cancelling the flowers would have been right. You want to save your grandmother pain, I understand that.
But the thing is, she’s going to feel that pain anyway. When the flowers come, she will very possibly be very upset.
But that’s a good upset. It’s a beautiful precious memory in amongst all the awfulness and the desolation and the loss
You want to protect her, because you love her. But you can’t protect her from this loss. By letting the flowers arrive, you’re letting this be a safe outlet if she needs it, or else a loving kind memory, very possibly both.
Don’t warn her. Let her have her anniversary gift just as she always has. I can imagine you want to warn her so she can prepare herself for the shock. But it may not be a shock, and in that case, your kindly meant warning will just steal the hot from her. Or it might be a shock, but all that warning her will do is to upset her earlier on.
Let her be sad. Let her feel the pain. Comfort her, of course, but to support her best you cannot interfere in her grief. You cannot carry it for her yourself although I’m sure in love you’d like to if you could. But it doesn’t work like that. Be there. Listen. Let her talk if she wants to, let her not talk if she doesn’t. But you can’t make this better for her, and by trying to protect her from it, you run the risk offer coming to resent you for it.
I’m sure in the days ahead there will be lots you can do for her. You can field phone calls if she wants you to, you can shield her from the outside world if that’s what she needs, you can take care of family arguments so she doesn’t have to be pulled into them or know they happened at all. But that’s running interference against the outsiders. Don’t try to run interference against the grief itself.
I’m sorry you are losing your grandfather.